Science 3

7. The Ideal Gas Law is an equation that relates the variables pressure, volume and temperature of a gas to the number of moles of gas present. PV = nRTPosttestMultiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. Who was the English scientist who made accurate observations on how pressure andvolume were related?a. Josef Boyle c. Robert Boyleb. Gay Lussac d. Jacques Charles2. When pressure on a gas is reduced to half, what happens to its volume?a. doubles c. stays the sameb. reduced to half d. rises, then falls3. In the equation for Boyle’s Law, P2 stands for:a. new pressure c. difference in pressureb. original pressure d. standard pressure, 1 atm4. The volume of a gas increases to 150%. What happens to its temperature?c. rises c. stays the samed. falls d. rises then falls5. The equation P1V1 = P2V2 is known as: c. Boyle's Law a. the Combined Gas Law d. the Ideal Gas Law b. Charles' Law6. The mathematical statement of Charles' Law isa. T1V1 = T2V2 c. T2V1 = T1V2b. T1V2 = T2V1 d. T2V2 = T1V17. Which value represents the standard temperature?a. 0 K c. 273 Kb. 273ºC d. 373 K8. “In the ideal gas equation, the constant R always has the numerical value of 0.08206, so it is called the Universal Gas Constant.” This statement: a. is true b. is false - 18 -

c. is true only for ideal gasesd. can neither be scientifically proven nor disproved9. The molar volume of a gas is the volume occupied at STP bya. 0.08206 mol of the gas c. 22.4 g of the gasb. 1 molecule of the gas d. 6.022 x 1023 particles of the gas10. Which of the following statements describes an ideal gas? a. behaves as predicted by the ideal gas law b. has molecules that do not attract one another c. has molecules that are considered volumeless d. all of the above11. At STP, samples of different gases having the same volume of 22.4 L will have different:a. masses c. pressureb. moles d. temperature12. Which statement best describes the relationship of the density of a gas to the temperature and pressure? a. Density increases with increasing pressure at a given temperature. b. Density decreases with increasing pressure at a given temperature. c. Density increases with increasing temperature at a given pressure. d. Density decreases with increasing temperature at a given pressure.13. At a given temperature, a gas can be compressed to a smaller volume by:a. increasing the pressure c. increasing the kinetic energyb. decreasing the pressure d. increasing the number of moles14. It’s 12 noon and you just bought a dozen balloons for your little sister’s birthday. Uponarriving at your house after traveling for more than an hour, you found that some of theballoons had burst (but the atmospheric pressure did not change at all). You accept thisas a consequence of:a. Boyles’ Law c. Gay-Lussac’s Lawb. Charles’ Law d. your own carelessness15. Which of the following statements about the density of a gas is correct? a. It is not affected by temperature. b. It is independent of pressure and temperature. c. It decreases with increasing temperature at constant pressure. d. It doubles when the volume of the container is doubled without a change in pressure or temperature.16. What will happen if we heat a 15 L sample of gas from 250 K to 290 K under constantpressure condition?a. The volume of gas increases. c. The number of moles of gas increases.b. The volume of gas decreases. d. The number of moles of gas decreases. - 19 -

17. A sample of carbon dioxide occupies 3 L at 35 ºC and 1 atm. What is the new volume ofthe gas at 48 ºC and 1.5 atm?a. 1.0 L c. 3.0 Lb. 2.1 L d. 4.2 L18. The J-shaped glass tube containing mercury and a sample of trapped gas was used by________ to measure the reduction in volume as more mercury is added.a. Boyle c. Avogadrob. Charles d. Gay-Lussac19. Real gases approach ideal behavior under which of the following conditions? a. at high pressure and high temperature b. at low pressure and high temperature c. near the boiling point of water d. real gases can never exhibit ideal behavior20. A graph showing the variation of volume (vertical axis) with temperature (horizontal axis) at constant pressure would look like: a. b. c. d.Error! Key to answers on page 23.Key to AnswersPretest 6. b 11. a 16. c 7. c 12. b 17. a 1. a 8. c 13. c 18. a 2. a 9. a 14. a 19. a 3. b 10. d 15. a 20. d 4. a 5. b - 20 -

Lesson 1Activity 1.11. barometer2. pressure3. Kelvin4. volume5. temperatureActivity 1.2Table of commonly used units for the temperature, pressure and volume of a gas. PHYSICAL QUANTITIES UNITSTemperature °C, °F, KPressure torr. Pa, kPa, mm Hg, cm HgVolume cm3, m3Activity 1.3 Marshmallows are mostly air and sugar. When the plunger is pulled away, thepressure is reduced, allowing the air inside the marshmallows to increase in volume.Self-Test 1.11. The gas will become more compressed when the weight of the passengers increase the pressure applied on the shock absorbers.2. d3. double4. 120 L5. 200 mlLesson 2Activity 2.11. The gases inside the balloons increased in volume causing the change in size in proportion to time immersed in water. The balloon dipped in hot water expanded while the one in cold water shrunk.2. The balloons reached normal size as they returned to room temperature.Activity 2.21. A small volume of gas inside the jar expanded and escaped when the lid was opened. - 21 -

2. The button stays up. During packing, the contents and the jar were hot. When lid is closed tightly and the jar is left to cool, a decrease in temperature causes the trapped gas to contract, pulling the button to the \"down\" position.Self-Test 2.1 1. pressure 2. bSelf-Test 2.2 1. 2.33 L 2. 29.3 K 3. temperature decreases by 70 KLesson 3Activity 3.1 The tension on the surface of the balloon increased the longer it was exposed to hot water. Heating caused the rise in the pressure of the gas inside the balloon, as predicted by Gay-Lussac’s Law. Volume was kept constant since the completely filled balloon could not expand anymore.Self-Test 3.1 approximately 8 balloons (since the volume at STP is 7.83 L)Self-Test 3.2 1. 4.0 atm 2. balloon will expand to 8.05 x 106 LLesson 4Activity 4.1Data on a sample of oxygen gas. nPT V R 150 ml 0.082060.00625 1.0 atm 293 K molSelf-Test 4.1 1. force exerted on the object divided by the area of the surface; 2. total space occupied by matter; for gases, volume is expressed in mL or L. - 22 -

3. physical property measuring the hotness or coldness of an object.4. states that the volume of a fixed quantity of gas at a constant temperature is inversely proportional to the pressure.5. states that the volume of gas at a constant pressure is directly proportional to its temperature.6. states the pressure a gas maintained at constant volume is directly proportional to its temperature.7. equation combining the relationships between pressure, volume and temperature.8. accepted experimental condition for the study of gases, 1 atm and 273 K9. ratio of the mass of the gas to its volume10. proportionality constant in the ideal gas equation, equal to 0.08206 L atm/mol KPosttest1. c 6. b 11. a 16. a2. a 7. c 12. a 17. b3. a 8. b 13. a 18. b4. a 9. d 14. b 19. b5. c 10.d 15. c 20. bReferencesBooks:Hill, J. (1981). Student’s guide to Brown and LeMay: Chemistry the central science. New Jersey: Prentice Hall.Magno, M.C., Tan, M.C & Punzalan, A.E. (1995). Science and technology for a better life series: Workbook (Chemistry). Manila: Diwa Scholastic Press, Inc.Moore, J.W., Stanitski, C.L., Wood, J.L, Kotz, J. C. & Joesten, M.D. (1998). The chemical world: concepts and applications. California: Brooks/Cole.Lemay, H.E., Beall, H., Robblee, K.M. & Brower, D.C. (2002). Chemistry: connections to our changing world. New Jersey: Prentice Hall.Petrucci, R.H., Harwood, W.S. & Herring, G. (2002). General chemistry: Principles and modern applications. New Jersey: Prentice Hall.Robinson, W.R., Holtzclaw Jr., H.F. & Odom, J.D. (1997). General chemistry. Massachusetts: Houghton Mifflin.Zumdahl, S.S. & Zumdahl, S.A. (2003). Chemistry. Massachusetts: Houghton Mifflin. - 23 -

Electronic Sources:The Ballad of a Gas. Poems by selected students in Chemistry 1992-93. Retrieved March 26, 2005, from http://teachers.net/lessons/posts/93.html.Image of Robert Boyle. Retrieved March 26, 2005, from http://www.woodrow.org/teachers/ chemistry/institutes/1992/BOYLE.GIF.Image of Jacques Charles. Retrieved March 26, 2005, from web.fccj.org/~ethall/gaslaw/ gaslaw.htm.Image of Gay-Lussac. Retrieved March 26, 2005, from http://www.ac-nancy-metz.fr/pres- etab/lapicque/Opinfo00/Genin/GayLussac.jpg. - 24 -

Module 10 What’s Inside the Atom? What this module is about Atoms are the basic building blocks of matter. This concept started around 440 B.C.and it changed and evolved throughout the centuries. For example, the ancient Greekphilosophers Leucippus and Democritus believed that atoms were solid. But in 1911,Ernest Rutherford proved that the atom was mostly empty space. In this module, we will present the evolution of the concept of the atom and themodern ideas of atomic structure. We will cover the following lessons:  Lesson 1 – Early Ideas about the Atom  Lesson 2 – The Subatomic Particles  Lesson 3 – Radioactivity and the Nuclear Model of the Atom  Lesson 4 – Atomic Spectra and the Atomic Structure The topics listed here seemed too “scientific” but the knowledge you will gain fromthem can be used in different aspects of our life. Ready? What you are expected to learn After reading this module, you are expected to have accomplished the following: 1. cite significant changes in the development of the atomic theory; 2. interpret the Law of Conservation of Mass, the Law of Definite Composition, and the Law of Multiple Proportion; 3. explain the statements in Dalton’s atomic theory; 4. state the importance of cathode rays and radioactivity in determining the structure of the atom; 5. state the characteristics of subatomic particles; 6. determine the number of protons, electrons, and neutrons of some elements; 7. define isotopes; 8. infer the relationship between atomic mass and relative abundance; 9. compute for the atomic weights of some atoms; 10. describe radioactivity; 11. explain why some radioactive elements are useful and dangerous;

12. state ways of protecting oneself from dangerous radiation;13. contrast different models of the atom; and14. discuss the influence of atomic spectra and electron spectra on the modern views of atomic structure. How to learn from this module This module is written to meet your special needs. This module allows you to learnat your own pace and space. But for you to gain the most out of this module, we suggestthat you do the following: 1. Find a quiet place where you can concentrate on reading this module. 2. Set-up a schedule for reading all the lessons in this module. For example, you may finish up to lesson 2 today, and then, tomorrow, you will tackle lessons three to five. And you will read the next lessons the day after. 3. Conduct the activities described in each lesson. These activities are simple and they can help you understand the concepts presented. 4. Answer the self-tests found at the end of each lesson. These self-tests gauge your understanding of the given lesson. They will tell you whether you have learned or you have not learned enough from the lesson. Do not forget also to answer the pretest and the posttest! Learning by yourself takes a lot of self-discipline and determination. I’m sure youhave these traits in you.What to do before (Pretest)Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. What happens to the mass of materials when they undergo a chemical reaction?a. Increase c. Remains the sameb. Decrease d. Ultimately disappears2. Which of these was not discovered using the cathode ray tube?a. X-rays c. Neutronsb. Protons d. Electrons -2-

3. Which describes the neutron? c. It was discovered by Goldstein a. It is negatively–charged d. It is lightest subatomic particle b. It is part of alpha–radiation4. What is the mass number of an atom of Berkelium that has 97 protons, 97 electrons, and150 neutrons?a. 53 c. 194b. 97 d. 2475. Which best describes isotopes? a. Same number of neutrons, different number of electrons b. Same number of neutrons, different number of protons c. Same number of protons, different number of electrons d. Same number of protons, different number of neutrons6. Which of these home appliances uses a cathode ray tube?a. Electric fan c. Refrigeratorb. Television d. Rice cooker7. Which can you observe in a radioactive material? a. It produces only a little amount of heat. b. The atom transmutes into another kind of atom. c. The radioactive atom absorbs alpha, beta, and gamma rays. d. The atom changes its phase and color as it releases radiation8. If there were five positive charges (+5) and three negative charges (–3) in a body, whatwould be the overall charge of the body?a. +3 c. –2b. +2 d. –39. What subatomic particles account for the mass of the atom?1. electron 2. proton 3. neutrona. 1 and 2 c. 1 and 3b. 2 and 3 d. 2 only10. Who is regarded as the father of modern atomic theory?a. Lavosier c. Daltonb. Rutherford d. Thomson Key to answers on page 27. -3-

Lesson 1. Early Ideas About the Atom Matter is basically made up of atoms. This theory started more than 2,400 years agoin Ancient Greece. But its rapid development only began about 1,000 years ago, whenJohn Dalton presented his own version of the atomic theory in 1803. In this lesson, we willpresent the original Greek concept of the atom, and that of Dalton.The Greek Concept During the ancient times (around 440 Democritus EpicurusB.C.), many of the “scientists” werephilosophers. They did not prove or disproveideas using experiments. Rather, they usedgood arguments to show that an idea was true.And so, Leucippus used logical reasoning tosupport the idea that “all things are basicallymade up of atoms”. There were noexperiments during his time. Of course, thismeans that Leucippus did not convince somephilosophers. Those who agreed with Leucippuswere called “atomists”. One of the first atomistswas Democritus. He was a student of Leucippus.Later on, another scientist-philosopher, Epicurus,improved the “atomos” concept.Let us understand the ideas of these atomists by conducting this simple activity: What you will do Activity 1.1 Cutting Matter1. Observe the head of a fried fish. a. Can you identify the lips? The eyes? The teeth?2. Using a small knife, chop the head of a fried fish into smaller pieces. a. Can you still identify the lips? The eyes? The teeth? b. If not, what do you now have?3. Grind the white eyeball into smaller pieces. Look at the newly formed pieces using a lens. a. Are the smaller pieces still similar with the original? Why? Why not? b. Can you still cut these pieces into smaller ones? c. Is it possible to keep on cutting and dividing these pieces? -4-

The answer of atomists to the question in # 3 c. is obviously “No”. They believe thatall matter is made of atoms, which are bits of matter. You can cut and divide matter untilyou reach a point where the pieces cannot be cut nor divided anymore. This means thatatoms cannot be split into smaller bits. According to Democritus, \"They have all sorts of shapes and appearances and different sizes.... Some are rough, some hook-shaped, some concave, some convex and some have other innumerable variations.\"Do you agree with them? Now let’s take a look at the Atomic Theory of John Dalton.Dalton’s Atomic Theory John Dalton is considered the Father of the Modern Atomic Theory. He was achemist who studied the works of Lavoisier and Proust. Antoine Lavoisier established theLaw of Conservation of Mass while Joseph Proust observed the Law of DefiniteProportions. Using these laws, Dalton formulated his atomic theory. Let us first take alook at these laws.Law of Conservation of Mass Law of Definite Proportions“The total mass of materials “The proportion by mass of thebefore a chemical reaction elements in a given compoundtakes place is exactly equal to is always the same.”the total mass of the materialsthat result after the reaction is It is also known as the “Law ofcompleted.” Constant Composition”. John Dalton believed that these two laws supported the idea of atoms. Heformulated an atomic theory that included the observations of Lavoisier and Proust. Thisatomic theory has these statements:#1 - All elements are composed of atoms, which are indivisible and indestructible particles. For example, an element, like gold, is made up of gold atoms. The atoms of gold cannot be destroyed nor divided to form other atoms. The Law of Conservation of Mass supports this statement. -5-

#2 - All atoms of the same element are exactly alike. This means that one atom of the element platinum looks exactly the same as any other atom of platinum. It also means that the mass of one atom of an element is exactly equal to the mass of another atom of the same element.#3 - All atoms of different elements are different. This statement is a follow-up of statement #2. It means that the atoms of the element silver are different from the atoms of the element oxygen. And one important difference among different atoms is their masses. The atoms of an element may have a greater or lesser mass than the atoms of another kind of element. Both statements #2 and #3 agree with the basic assumption of the Law of Definite Proportions: that the mass of atoms does not change.#4 - The joining of atoms of two or more elements form compounds. When an atom of one kind of element is joined with another atom of another kind of element, a compound is A water molecule formed. Dalton further stated that in any compound, the atoms of the different elements in the compound are joined in a definite whole-number ratio. For example, in the compound water, a particle of water is made up of one atom of oxygen and two atoms of hydrogen. The ratio of oxygen to hydrogen is 1:2. Some elements also show that they form various ratios. For example, iron can forma compound with oxygen in the ratio of 1:1. This means that for every atom of iron, there isone atom of oxygen. At the same time, iron can form another compound with oxygen in theratio of 2:3. This means that for every two atoms of iron, there will be three atoms ofoxygen. In other words, iron can form two different ratios with oxygen. Other metals likecopper and chromium also show this phenomenon. Such phenomenon resulted to the Lawof Multiple Proportions. What you will do Self-Test 1.1Directions: Answer these questions briefly.1. Identify the similar ideas between the Greek concept of the atom and the statements in Dalton’s atomic theory. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ -6-

2. Explain the importance of the works of Lavoisier and Proust to the atomic theory of Dalton. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ Key to answers on page 27.A Scientist Always Asks A Question Asking questions is a good exercise to sharpen your scientific thinking skills. Onegood question is: Would Dalton have formulated the atomic theory if Lavoisier did notestablish the Law of Conservation of Mass? Now, it’s your turn. Ask a good question now: ___________________________________________________________________________Lesson 2. The Subatomic Particles What’s inside the atom? We already know that an atom is not as solid as a toymarble. In fact, three different subatomic particles inside it have been discovered.“Subatomic” means “inside the atom”. These are the protons, the electrons, and theneutrons. But first, we must get acquainted with an instrument that made the discovery ofsubatomic particles possible: the cathode ray tube.The Cathode Ray Tube (CRT) The CRT is a glass tube with two electrodes. One electrode is positive and it iscalled the anode. The other electrode is negative and it is called the cathode. A gas is usually placed inside this tube and electricity is passed through it. As aresult, light rays are released from the negative electrode (cathode) and hit the positive -7-

electrode (anode). These rays are obviously negatively charged since they come from thecathode and move towards the anode. A scientist named Julius Plucker first identified thecathode rays, and another scientist named Sir William Crookes confirmed this. He inventedthe Crookes tube, which is actually the prototype of the cathode ray tubes. The cathode raytube is used in neon signs. Karl Ferdinand Braun further improved the CRT, and his “Brauntube” is the prototype of today’s television tubes, radar tubes, and computer monitors.Because of the CRT, Roentgen discovered the x-rays. And still because of the CRT, thesubatomic particles electrons and protons were discovered.Subatomic ParticlesHere is a table comparing the three subatomic particles. Table 2.1Particle Symbol Discoverer Charge MassElectron e− 9.11 x 10–31 kgProton p+ J.J. Thomson, 1897 Negative 1.3626231 x 10–27 kgNeutron n0 1.6749 x 10–27 kg E. Goldstein, 1886 Positive J. Chadwick, 1932 No charge All atoms have a positive nuclear charge due to the presence of protons. Thenumber of protons in an atom determines the positive nuclear charge of an atom. Protonsalso determine the atomic number (Z) of an element. We can tell how many protons anatom of an element has by knowing its atomic number. For example, the element beryllium(Be) has an atomic number of 4. An atom of beryllium has four protons. The elementKrypton (Kr) has an atomic number of 36, and one atom of Krypton has 36 protons. The proton is 1,836 times heavier than the electron. When electrons and protons areplaced side by side, the proton will be as big as a house, while the electron will only be oneof its light switches. The difference in the number of protons and number of electrons determines theoverall charge of the atom. For example, if an atom has 4 protons and 4 electrons, theoverall charge of the atom is zero. But if there are 6 protons and 5 electrons, the overallcharge of the atom is +1. It is positive because there are more protons than electrons. Ifthere are 12 protons and 14 electrons, the overall charge of the atom is –2. It is negativebecause there are more electrons than protons. Together with protons, neutrons make up the mass number (A) of an atom. Forexample, the element calcium has a mass number of 40 and an atomic number of 20. Thismeans that the calcium atom has 20 protons. To determine the number of neutrons, usethis formula: Mass number – atomic number = number of neutrons 40 – 20 = 20The calcium atom also has 20 neutrons. -8-

Now let’s try to visualize what the atom looks like. What you will do Activity 2.1 Atom Assembly Let’s attempt to assemble the composition of the Boron atom. The atomic number ofBoron is 5, the mass number is 11, and the overall charge of the atom is zero. This meansthat Boron has 5 protons, 5 electrons, and 6 neutrons. In a plate, place 5 pieces of calamansi fruits. These will be our protons. Then place6 pieces of lanzones fruits. These will be our neutrons. Then add 5 pieces of rice grains.These will be our electrons. Now try to assemble the components of a Fluorine atom. Its atomic number is 9, itsmass number is 19, and its overall charge is –1. Describe the contents of your plate. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________What you will doSelf-Test 2.1Directions: Fill up this table. Consult a periodic table to know the symbol of the elements.Element Element Atomic Mass Charge No. of No. of No. of Name Symbol Number, Number, of the protons Electrons Neutrons atom Silicon Z A Silver 14 28 –4Strontium 108 0Samarium 47 0 38 36 50 88 62 Key to answers on page 28. -9-

A Scientist Always Asks A Question Asking questions is a good exercise to sharpen your scientific thinking skills. Onegood question is: Why are there three subatomic particles? Why not two, or four? Now, it’s your turn. Ask a good question now: ___________________________________________________________________________Atomic Mass and Isotopes In the periodic table, we find “atomic mass”. Is this exactly the same as “massnumber”? No, these two terms are not the same due to the existence of isotopes. Whatare isotopes? What you will do Activity 2.2 The Same But Different Study two potatoes. These two are the same simply because both are potatoes.But, they are also different. List four things that make one potato different from another. 1. __________________________________ 2. __________________________________ 3. __________________________________ 4. __________________________________ Just like the potatoes, isotopes are atoms of the same element but they havedifferent mass numbers. This means that two atoms can have the same number of protons,but have different numbers of neutrons. For example, the hydrogen element has threedifferent isotopes. The isotopes of hydrogen are namedprotium, deuterium, and tritium. All of themhave an atomic number of 1. This means that allof them have one proton. But protium has a massnumber of 1. It has no neutron. The deuteriumhas a mass number of 2. It has one neutron. Andtritium has a mass number of 3. It has twoneutrons. The existence of isotopes led to the existence of atomic mass. Atomic mass isdetermined by how much percentage or relative abundance a certain isotope exists in - 10 -

nature. This can be computed by using this formula:Atomic Mass = Σ (mass number of one isotope x relative abundance) The symbol Σ reads “summation”. It means that we will add the products of the massnumber and relative abundance of the isotopes. For example, nitrogen has two isotopes, 14N and 15N. The 14N or N–14 has a relativeabundance of 99.63%, while the 15N or N–15 has a relative abundance of 0.37%. Tocompute for the atomic mass,Atomic mass = (0.9963 x 14) + (0.0037 x 15) = 13.9482 + 0.0555 = 14.0037Some Amazing Isotopes Some isotopes can save lives! Isn’t that amazing? Isotopes are used to find out if aperson is sick or not. This is called radiation detection. Here are some isotopes and theiruses in medicine. Table 2.2 Isotopes in the world of medicine Isotope Uses in MedicineIodine – 131  Used to determine the size, shape and activity of theCobalt – 57 thyroid gland  Treats cancer located in the thyroid gland  Controls a hyperactive thyroid  Determines whether you have enough intake ofCobalt – 60 vitamin B12Gadolinium – 153  Used for radiation therapy treatment of cancerTechnetium – 99  Used to determine bone mineralization especially forCarbon –11 women who suffer from osteoporosisChromium – 51  Used to detect blood flow patterns in the heartPhosphorus – 32  Scans the brain, liver, kidney, and lungs  With the PET (positron emission tomography) technology, it is used to scan and measure processes that occur in the body  Determines the volume of red blood cells and the total volume of blood  Detects skin cancer or cancer of body tissues that have been exposed to surgery - 11 -

What you will do Self-Test 2.2Directions: Compute for the atomic mass of these isotopes 1. 16O (99.76%), 17O (0.04%), and 18O (0.20%) 2. 32S (95.06%), 33S (0.74%), 34S (4.18%), and 36S (0.02%) 3. 35Cl (75.53%), and 37Cl (24.47%) Key to answers on page 28.A Scientist Always Asks A Question Asking questions is a good exercise to sharpen your scientific thinking skills. Onegood question is: We have three isotopes of hydrogen on planet earth. Will we find afourth isotope on another planet, like Mars or on a moon, like Titan? Now, it’s your turn. Ask a good question now: ____________________________________________________________________Lesson 3. Radioactivity and the Nuclear Model of the Atom Some isotopes constantly release their protons, electrons, and neutron. As thesesubatomic particles are released, tremendous amounts of energy are also emitted. Thereleased particles and the energy that goes with them are called radiation.Important historical events  In November 1895, Wilhelm Conrad Roentgen discovered the x-rays.  Henri Becquerel discovered radioactivity. Radioactivity is the spontaneous emission of radiation by some elements. These are called radioactive elements.  Pierre Curie and Marie Sklodowska Curie also investigated the phenomenon of radioactivity, using uranium ore. As a result, they discovered the elements polonium and radium, which were also radioactive elements.  Ernest Rutherford, the father of nuclear physics, observed that radioactive elements such us uranium and thorium became different elements. He called this process as radioactive decay. - 12 -

Becquerel Marie Curie Pierre Curie RutherfordRadioactive Decay According to Rutherford, there are three types of radiation based on the material thatthey can pass through. These are alpha (symbol is α), beta (symbol is β), and gamma(symbol is γ). Observe this illustration. The alpha radiation is made of two protons and two neutrons.This means that it is big and positively charged. It cannot pass throughtissue. But the alpha radiation is most dangerous especially whentaken inside the body. It can damage living cells and body tissues.This is why the alpha radiation is not used in medicine. The beta radiation is made of an electron. It is very small andnegatively charged. It can pass through tissue but not through a metallike aluminum. It can also damage body tissues. The gamma radiation is radiant energy coming from the atom.It is a high-energy radiation and has no charge. Because it is neutral, itcan pass through paper, metal, and even through thick concrete.Gamma rays are used in medicine. But still it is the most dangeroustype of radiation simply because only thick lead can stop it.Detecting Radiation Radiation from radioactive elements is dangerous. To avoidoverexposure to it, scientists and doctors who work using radioactiveelements have ways of detecting radiation. - 13 -

Photographic Emulsion - This is an old technique thatwas used by Becquerel. The radiation from elements affect thephotographic film in the same way that light can affect the film. If you have the chance to observe nuclear scientists, youwill notice that photographic films or papers are clipped to theirlaboratory gown. These are called dosimeters. Big changes inthe dosimeter mean that too much radiation reached it. Fluorescent Materials - These materials, when hit by radiation, transform theradiation into light energy that can be seen by the naked eye. One example is the luminouspaint used in clocks. The Cloud Chamber - It is an apparatus developed by T.R. Wilson in 1911. Asample of air is saturated with water vapor, and then, this is cooled and a cloud is formed.When a radioactive material is placed in this chamber, thin lines of fog can be seen to comeout of it. The Geiger Counter - This instrument is made of two parts, a metal guard and adetector. The metal guard is shaped like a tube that is filled with gas. This metal guard hasa “window” where radiation can come in and ionize the gas inside. The ionized gasproduces a current and this current reaches the detector. Some detectors light up or giveflashes of light, while other detectors produce clicking sounds.Half-Life of Radioisotopes Radioisotope is a short name for “radiation-active isotopes”. Radioactivity results inthe transmutation of a radioisotope into another element. For example, some atoms ofuranium transmute and become atoms of element lead. The amount of radioactive materialthat transmutes into another element can be computed based on its half-life. The half-life is the time that it takes one-half of the given starting weight ofcertain radioactive material to change into another material. The half-lives ofradioactive materials were determined through experiments. Here are the half-lives of someradioisotopes: Table 3.1 Half-lives of some radioisotopesRadioactive Half-life Radioactive Half-life element elementTritium 12.3 years Uranium – 238 4.5 billion yearsCobalt – 60 5.25 years Mercury – 190 20 minutesCarbon – 14 5,730 years Krypton – 81 13 secondsMolybdenum – 99 67 hours Technetium – 99 6 hours For example, we have 20 grams of mercury–190. Its half-life is 20 minutes. Thismeans that after 20 minutes, half of our radioactive mercury sample was transmuted into - 14 -

other elements. As a result, only 10 grams of mercury–190 are left. Then, after another 20minutes, half of the 10 grams of mercury–190 were changed, leaving 5 grams of mercurybehind.What you will doActivity 3.1 Graphing the Radioactive Decay Your objective in this activity is to create a line graph that will show the radioactivedecay of a radioisotope. You will need a pencil and a graphing paper.1. The horizontal or x-axis will represent the time that passed or elapsed.2. The vertical or y-axis will represent the amount of radioisotope.3. Use the data below.Amount of Tc-99 Hours that passed Amount of Tc-99 Hours that passed 80 g 0 5 24 40 6 2.5 30 20 1.25 36 10 12 0.625 42 184. Describe the graph that you created. What kind of line was formed? _________________________________________________________________5. Is it possible to transmute ALL the technetium–99? Why? Why not? _________________________________________________________________ What you will do Self-Test 3.1A. Direction: Each of the items below describes a type of radiation. Write α if it describes an alpha particle, β if it describes a beta particle, or γ if it describes a gamma particle. ______ 1. It is positively charged. ______ 2. It has no charge. ______ 3. The heaviest type of radiation. ______ 4. The type of radiation that has no mass. ______ 5. It is composed of electrons.B. Direction: Answer these problems about half-life. Refer to the Table 2. 1. If we have 100 grams of carbon–14, how long will it take this radioisotope to become 25 grams? - 15 -

2. A scientist placed 60 grams of Krypton–81 inside a cloud chamber. How much Krypton–81 will be left after 1 minute and 5 seconds? 3. A certain radioisotope originally weighed 200 grams. After 4 hours, only 3.125 grams were left. What was its half-life? Key to answers on page 28.The Nuclear Atom Remember your activity in Lesson 2 when you “assembled an atom”? We couldn’tbe sure if we are going to place the “protons” beside the “neutrons” or place an “electron”between the “proton” and a “neutron”. In this lesson, we will have an idea where thesesubatomic particles are located though not the exact location, but an estimate only. First, let’s recall a little history. During Democritus’ time, atoms were thought to havedifferent sizes, shapes, and weights. This was changed during Dalton’s time. According tohim, atoms are small spheres. Do you think Dalton was right? When J.J. Thomsondiscovered the electrons, some scientists believed that the atom is like a piece of bread withraisins stuck to its surface. The “piece of bread” is the positively charged body of the atomand the “raisins” are the negatively charged electrons. And then, Rutherford conducted the alpha–gold foil experiment. The surprisingresults of this experiment radically changed the way scientists view the atom. Tounderstand one result of the alpha–gold foil experiment, do this activity first. What you will do Activity 3.2 Positive and Positive Poles A magnet has two poles called the North (marked N) and the South (marked S)poles. Let’s assume that the North pole is the “positive” end of the magnet and the Southpole is the “negative” end. Place the two positive ends near each other. Observe whathappens. When similar poles of the magnet are placed near each other, the magnets tend tomove away from each other. This is because similar poles repel each other. In the sameway, like charges also repel each other. Let’s remember this when analyzing the alpha –gold foil experiment. - 16 -

The Alpha-Gold Foil ExperimentThe alpha rays are bigpositively charged particles that aremoving at very fast speeds. If theserays hit an object, there would bemuch damage. And in theexperiment, alpha rays were used tobombard a very thin gold foil.Probably, the plan of Rutherford andhis colleagues were to smash theatoms of the gold foil. And so, the setup was like this: The apparatus was a vacuum to prevent atoms of the air to interfere with theexperiment. A microscope was placed slightly behind the gold foil so that the scientistscould safely observe what would happen once the alpha rays hit the foil. The microscopecouldn't be directly behind the foil because the scientists didn’t want the alpha rays or thesmashed atoms of gold to come directly straight to them. From the source, alpha rays were released and they did hit the gold foil at highspeeds. But Rutherford and his team of scientists were surprised at the results of theexperiments. Their observations from the experiment were:1. Most of the alpha rays just passed through the gold foil.2. A small portion of the alpha particles was deflected.3. An even smaller portion of the alpha particles bounced right back. Table 3.2 shows the conclusions made by Rutherford based from what he observedin the experiment.Table 3.2 Conclusions from the alpha – gold foil experimentObservations ConclusionsMost of the alpha rays just Most of the atom is just empty space.passed through the gold foil. (How else could the alpha particles pass through?)A small portion of the alpha There is a positive charge inside the atom thatparticles was deflected. occupies a very small space. (The small positively charged core inside the atom repelled and deflected the positively charged alpha rays)An even smaller portion of The alpha particles that bounced back werethe alpha particles bounced traveling directly straight into the positivelyright back. charged core. - 17 -

To illustrate what happened,study this diagram. Rutherfordcalled the positively charged core inthe atom as the nucleus of theatom. And so, another structure ofthe atom was made.The Nuclear Model of the Atom The new model of the structure of the atom is called the nuclear model. This modeldescribes the atom as having a nucleus at its center. The nucleus of the atom does not have a fixed boundarylike the nucleus of a cell. The protons and the neutrons arefound together in this nucleus. They are called nucleons. Anattractive force called the nuclear force holds them together. Rutherford estimated the radius of the nucleus to be 3 x10–14 m. Researches of scientists in the later years establishedthat the radius of the nucleus is about 1.5 x 10–14 m. Rutherfordwas almost right. The electrons in the nuclear model were assumed to just move around the nucleus. What you will do Self-Test 3.2Directions: Draw nuclear models for the atom of the following elements.Atom of Carbon Atom of Sodium Atom of Sulfur Atom of Neon Key to answers on page 28. - 18 -

A Scientist Always Asks a Question Asking questions is a good exercise to sharpen your scientific thinking skills. Onegood question is: Is it possible to have two nuclei in an atom? Now, it’s your turn. Ask a good question now: ___________________________________________________________________________Lesson 4. Atomic Spectra and the Atomic Structure Up until now, we can think of subatomic particles as small solid spheres. Strangely,a scientist named Louis De Broglie proposed a theory that electrons showed characteristicssimilar to light. But light is a form of energy. Is this possible? Yes it is. De Broglie’s theorywas proven by an experiment conducted by Davisson and Germer. In this lesson, we willpresent some concepts about light and explain how electrons could behave like light. What you will do Activity 4.1 Observing Rainbows To understand more about the nature of light, we will first observe a rainbow. Arainbow usually appears after a rain. What if there is no rain? Don’t worry; we can stillcreate a rainbow. All you need is a basin half-filled with water, a mirror, and a plain wall. Go near the wall and place the basin of water on the ground. Make sure that you dothis when the sun is high in the sky. Position the mirror above the water of the basin so thatit will catch the rays of the sun and reflect it to the water. A rainbow will appear on the wall. Observe this rainbow. 1. How are the colors arranged? _________________________________________________________________ 2. Will the arrangement remain the same if you move the mirror upside down? Why? Why not? _________________________________________________________________ _________________________________________________________________ 3. Will the arrangement remain the same if you go to another wall? Why? _________________________________________________________________ _________________________________________________________________ - 19 -

The Electromagnetic Spectrum The rainbow showed that the colors oflight are arranged in a specific way. Tounderstand why, we must think of light as amoving wave. A wave has five knownproperties. These are crest, trough,wavelength, amplitude, and frequency. The crest is the highest point of a wave while the trough (pronounced as “truf”) is thelowest point. The distance between two crests (or two troughs) is the wavelength. If ahorizontal line is drawn from the crest and another from the trough, the distance betweenthese two lines is the amplitude. Now let’s imagine this wave to move to the right. At acertain point, crests after crests are going to pass through. The number of crests (ortroughs) that will pass through our imaginary point within a period of time is the frequency. The colors of the rainbow have different wavelengths. Red has the longestwavelength and violet has the shortest. A wave also has a specific amount of energy. Lightwaves with longer wavelengths have lesser energy than light waves with shorterwavelengths. In the colors of the rainbow, red has the least energy while violet has thegreatest energy. The colors of the rainbow are just a small part of the electromagnetic spectrum.Study this diagram. Beyond the color red is the infrared or heat radiation. The waves of infrared havelonger wavelengths and lesser energy. Beyond the color red is the ultraviolet radiation. Thewaves of UV rays have shorter wavelengths and greater energy. The large amount ofenergy that the UV rays have can harm body tissues.Bohr’s Ideas and Energy Levels Some elements emit certain light energy when they are heated. For example, theelement lithium, when heated produces a particular red color; cesium, when heated,produces a blue color; barium produces a green color; and potassium produces a violetcolor. This phenomenon led Niels Bohr to the idea that the electrons in an atom are foundin certain distances from the nucleus. These “distances” are related to the energy that anelectron has, and these are called energy levels. If the atom is not yet heated, the electron stays at its usual ground state. Then,when the atom is heated, the electron absorbs energy. Since it now has more energy, it - 20 -

jumps to a higher energy level. This electron is now at its excited state. Of course, thisexcited state is unusual and not stable. And so, the electron must go back to its originalenergy level. To do so, the electron must release its extra energy. The released energy isin the form of light. We see it as the element’s color when it is heated. But not all light released by the atom can be seen by our eyes. To see all the lightenergy released by atoms, an instrument called spectroscope is used.Emission and Absorption Spectra The light released by an element that is heated is called its emission spectrum.This is the light detected by a simple spectroscope. At the same time, an element is alsocapable of absorbing energy. An “absorption spectroscope” is an instrument that detectsthe ability of an atom’s electrons to absorb a certain amount of energy. This absorbedenergy is called the absorption spectrum. Instead of colors that appear, this instrumentshows lines instead. When you pursue a science course in college, you will learn moredetails about how a spectroscope works. But right now, let us see what an absorptionspectrum looks like. This is an absorption spectrum, which is also called a line spectrum. The numbersare the wavelengths of light in Angstrom units. One Angstrom is equal to 1 x 10–10 meters.Study some spectra below. - 21 -

Each element has its own unit line spectrum. As technology improved, it is nowpossible to see the spectrum of electrons! The technology is called photoelectronspectroscopy.Electron Spectra In photoelectron spectros-copy, the atom of an element in itsgaseous state is hit by radiation.The radiation has enough energy toremove an electron from any energylevel. Of course, when the electronsare nearer to the nucleus, it will takea greater amount of energy to ejectthem. If the electrons are fartherfrom the nucleus, a lesser amount ofenergy is needed to eject theelectron.The energies of the ejectedelectrons are measured by thephotoelectron spectrometer. Aphotoelectron spectrum isproduced. Refer to the spectra in the next page as you continue reading so that we willhave a clearer image of electrons in their energy levels. Hydrogen has one electron and this is why we have only one “peak” in its spectrum.Helium has two electrons, but its spectrum shows only one peak. This peak is higher thanthat of hydrogen. This means that there are two electrons having the same energy. It alsomeans that helium’s two electrons are found on the same energy level, the first energy level. - 22 -

Neon has three peaks. The first two peaks are as high as the peak of helium. Thismeans that each of the first two peaks of Neon has two electrons. The first peak needed about 84.0 MJ/mol of energy, while the second peak neededabout 4.68 MJ/mol of energy. This means that the two electrons in the first peak are foundin one energy level, and the two electrons in the second peak are found in another energy - 23 -

level. The electrons in the first peak are nearer to the nucleus since it needed greaterenergy. The third peak of neon is about three times higher than the first two. This meansthat this peak represents six electrons of neon. Notice the amount of energy it needed. Thesix electrons only needed 2.08 MJ/mol of energy. This is very near the amount of energyneeded in the second peak (4.68 MJ/mol). This means that the electrons in the secondpeak and in the third peak are found in the same energy level. But why are there two peaksin that energy level? The only reason is that this energy level has sublevels of energy. Wecan conclude that Neon has two energy levels. The first energy level contains twoelectrons, and the second energy level contains a total of eight electrons. There are alsotwo sublevels in the second energy level. Two electrons are found in the first sublevel, andthe six electrons are found in the second sublevel. Based on the spectrum, sodium has three energy levels. The first energy level hastwo electrons needing energy equal to 104 MJ/mol. The second energy level has sublevelsagain. The first sublevel has two electrons needing energy equal to 6.84 MJ/mol, and thesecond sublevel has six electrons needing energy equal to 3.67 MJ/mol. The third energylevel has one electron only. Notice how small the peak is. It also needed the least amountof energy, only 0.50 MJ/mol. This means that this sole electron is found in the outermostenergy level, the farthest from the nucleus. What you will do Self-Test 4.1Directions: True or False. Write T if the statement is true, and F if it is false.__________ 1. The highest point in a wave is called the frequency.__________ 2. The green color has a longer wavelength than the blue color.__________ 3. The ultraviolet rays have more energy than x-rays.__________ 4. Three electrons can occupy each orbital.__________ 5. The f-orbital has more orientations than the p-orbital.__________ 6. An energy level can have two or more sublevels.__________ 7. An electron at its excited state has less energy than when it is at the ground state.__________ 8. Radiation can eject electrons from its energy level.__________ 9. Two elements can have the same absorption spectra.__________ 10. Two electrons can have the same amount of energy. Key to answers on page 29. - 24 -

A Scientist Always Asks A Question Asking questions is a good exercise to sharpen your scientific thinking skills. Onegood question is: What would have happened if photoelectron spectroscopy wasnever invented? Now, it’s your turn. Ask a good question now: ___________________________________________________________________________ Let’s Summarize In this module, you have learned the following important concepts: 1. According to the modern atomic theory, all elements are composed of atoms. Compounds are formed when two or more atoms of different elements join together. 2. The Law of Conservation of Mass states that the total mass of the reactants before a chemical reaction takes place is exactly equal to the total mass of the products of the reaction. 3. The Law of Definite Proportions states that the proportion by mass of the elements in a given compound is always the same. 4. Cathode rays and radioactivity helped in determining the structure of the atom. 5. The subatomic particles are electrons, protons, and neutrons. Electrons are negatively charged; protons are positively charged; and neutrons have no electrical charge. 6. The positive nuclear energy of an atom is due to the presence of protons. Protons also determine the atomic number of an element. 7. The difference in the number of protons and number of electrons determines the overall charge of the atom. 8. Protons and neutrons make up the mass number of an atom. 9. Isotopes are atoms with the same atomic number but different mass numbers. 10. The atomic mass of an element is determined by the isotopes’ relative abundance in nature and the mass numbers of each isotope. 11. Many isotopes are used to diagnose and/or treat diseases. 12. Radioactivity is the spontaneous emission of radiation by a material. 13. There are three types of radiation based on the material that they can pass through. These are alpha (symbol is α), beta (symbol is β), and gamma (symbol is γ). 14. Radiation from radioactive elements is dangerous. Radiation can be detected by using dosimeters, fluorescent materials, cloud chambers, and Geiger counters. 15. The half-life is the time that it takes one-half of the given starting weight of certain radioactive material to change into another material. - 25 -

16. The alpha-gold foil experiment led to the development of the nuclear model of the atom. The atom has a small nucleus that contains the protons and the neutrons. Most of the atom is empty space. The electrons are moving around the nucleus.17. A wave has five properties: crest, trough, wavelength, amplitude, and frequency.18. When heated, the electrons of an atom absorb energy and jump from one energy level to a higher energy level, transforming from the ground state into the excited state.19. The light released by an element that is heated is called its emission spectrum. This light is the one that is detected by a simple spectroscope.20. Absorption spectroscopy detects the ability of an atom’s electrons to absorb a certain amount of energy called the absorption spectrum.PosttestMultiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. The element X in a compound was involved in a chemical reaction. After the reactionwas completed, which of these would likely happen to the mass of element X?a. It will increase c. It will be doubledb. It will disappear d. It will remain the same2. All these were discovered because of the cathode ray, excepta. X-rays c. Neutronsb. Protons d. Electrons3. Which statement describes the neutron? c. It was discovered by Rutherford. a. It is positively-charged. d. It is the heaviest subatomic particle. b. It is part of a gamma radiation.4. What is the mass number of an atom of the artificial element Promethium that has 61protons, 61 electrons, and 84 neutrons?a. 23 c. 145b. 122 d. 2065. Which best describes isotopes? c. Same number of neutrons, different number of electrons d. Same number of neutrons, different number of protons e. Same number of protons, different number of electrons f. Same number of protons, different number of neutrons - 26 -

6. Which of these technologies uses a cathode ray tube?a. Cellular phone c. Microwave ovenb. Computer monitor d. Air-conditioning unit7. Which does NOT happen to a radioactive material? a. It produces a tremendous amount of heat. b. The atom transmutes into another kind of atom. c. The radioactive atom absorbs alpha, beta, and gamma rays. d. It emits high–energy waves that can pass through thick concrete.8. If there were six positive charges (+6) and three negative charges (–3) in a body, whatwould be the overall charge of the body?a. +3 c. –2b. +2 d. –39. How do we call the protons and neutrons that are found together in the nucleus?a. Nuclei c. Mass Numberb. Nucleons d. Atomic Mass10. He is one of the first atomist who believed that all things are made up of atoms.a. Dalton c. Goldsteinb. Democritus d. Rutherford Key to answers on page 29. Key to AnswersPretest1. c 6. b2. c 7. b3. b 8. b4. d 9. b5. d 10. cLesson 1Self-Test 1.11. Similar ideas include: 1) matter is composed of atoms; 2) indestructibility and invisibility of the atom; and 3) atoms of different elements have different weights or masses - 27 -

2. Lavoisier’s Law of Conservation of Mass, and Proust’s Law of Definite Proportion has the same assumptions about the atom as in the Atomic Theory of Dalton. These assumptions include: 1) Atoms cannot be destroyed; and 2) Atoms have constant mass.Lesson 2Self-Test 2.1 Element Element Atomic Mass Charge No. of No. of No. of Name Symbol Number, Number, of the protons Electrons Neutrons atomSilicon Si Z A 14 18 14Silver Ag 14 28 –4 47 47 61Strontium Sr 47 108 0 38 36 50Samarium Sm 38 88 +2 62 62 88 62 150 0Self-Test 2.2 1. 15.9994 a. m. u 2. 32.064 a. m. u 3. 35.453 a. m. uLesson 3Self-Test 3.1 B. 1. 11, 460 years 2. 1.875 grams A. 1. α 3. 40 minutes 2. γ 3. α 4. γ 5. βSelf-Test 3.2 Atom of Carbon Atom of Sodium - 28 -

Atom of Sulfur Atom of NeonLesson 4 6. T 7. FSelf-Test 4.1 8. T 9. F 1. F 10. T 2. T 3. F 6. c 4. F 7. c 5. T 8. a 9. bPosttest 10. b 1. d 2. c 3. d 4. c 5. dReferencesHill, J. & Kolb D. (1995). Chemistry for changing times. (7th ed.) NJ: Simon & Schuster (Asia) Pte.Ltd. - 29 -

Module 11 Atoms in the Periodic Table What this module is about In chemistry, the generalization that there is a recurring pattern in the properties ofthe elements is explained through an organized table called the PERIODIC TABLE.DMITRI MENDELEEV organized the order of elements in the periodic table according totheir atomic numbers. Later, great progress was made in explaining the periodic law interms of the electronic structure of atoms and molecules. As you study the features of the periodic table, the simplest question you must ask is“How are elements arranged?” Studying the chemistry of every element in the periodictable is not a simple thing to do. By reading this module it would be a lot easier to understand how the elements arearranged. This module will help you fully understand the similarities and differences amongatoms and why elements are grouped together in a table. This module also includes thehistorical background on how the Periodic Table was formed. You will study the following lessons in this module:  Lesson 1 – The Periodic Table and the Symbols of Elements  Lesson 2 – Properties of Elements in the Periodic Table  Lesson 3 – The Electron Configuration and Order of Elements  Lesson 4 – Importance of Some Elements in Industry What you are expected to learn After going through the module, you are expected to: 1. name the elements given the chemical symbol; 2. state the basis of the arrangement of elements in the periodic table ; 3. use the periodic table to predict the properties of elements; and 4. be familiar with the properties of some elements and their uses in industry.

How to learn from this moduleHere’s a simple guide for you in going about the module:1. Read and follow the instructions carefully.2. Answer the pre-test in order to determine how much you know about the lessons in this module.3. Check your answers with the given answer key at the end of this module.4. Read each lesson and do the activities that are provided for you.5. Perform all the activities diligently to help and guide you in understanding the topic.6. Take the self-tests after each lesson to determine how much you understood the topic.7. Answer the posttest to measure how much you have gained from the lessons. Good luck and have fun!What to do before (Pretest)I. Multiple Choice. Choose the letter of the best answer. Write the chosen letter on aseparate sheet of paper.1. Among the scientists who were responsible for the development of the periodic table are:I. Dmitri Mendeleev II. Johann Dobereiner and III. John Newlands. Arrange their namesin order of the history of the development of the periodic table.a. I , II, III c. III, I, IIb. II, III, I d. III, II, I2. Who was the scientist who arranged the elements according to groups of three?a. John Dalton c. Dmitri Inovich Mendeleevb. Johann Wolfgang Dobereneir d. John Alexander Newlands3. All the elements belonging to Group II A have ___ electron(s) in its outermost shell.a. 1 c. 3b. 2 d. 44. The number of protons in an atom represents thea. ionization energy c. atomic numberb. electronegativity d. atomic mass -2-

5. Which of the following is an alkali metal? c. Li a. Ba d. Fe b. Pb6. Which of the following decreases across a period on the periodic table?a. atomic radius c. electron affinityb. ionization energy d. electronegativity7. Which of the following statements is NOT correct? a. Atoms become smaller as one moves down a group. b. Atoms become smaller as one moves to the right across a period. c. Atoms become larger when electrons are removed. d. The size of an atom is not a factor in arranging the elements in the periodic table.8. Who was the scientist who arranged the elements in horizontal rows according toincreasing atomic masses?a. John Dalton c. Dmitri Inovich Mendeleevb. Johann Wolfgang Dobereneir d. John Alexander Newlands9. Which orbital is being filled in the lanthanide series of elements?a. 4f c. 5fb. 4d d. 5d10. Which of the following sets is a set of all metals?a. S, Li, C c. K, Li, Nab. He, Be, Ne d. Ca, Cr, Co11. Each vertical column of the periodic table is calleda. a period c. a groupb. a row d. none of these12. What family of elements includes helium and neon?a. noble gases c. halogensb. alkali metals d. none of these13. What family of elements includes fluorine and chlorine?a. noble gases c. halogensb. alkali metals d. none of these14. How many electrons are there in an atom of an element in Period 4 group VII A?a. four c. sixb. five d. seven15. Which element reacts by gaining an electron?a. He c. Fb. Be d. Na -3-

II. Fill in the blank with the correct word(s).1. The first scientist to arrange the elements in the periodic table by groups of eight (8) was ___________________.2. The number of electrons distributed in each energy level of an atom is indicated by the _____________________________.3. Elements having some metallic and nonmetallic properties are called ____________________.4. Elements belonging to Family VIII A are called ____________________.5. In an electron configuration, the number 3 in 1s22s22p63s1 represents the _________ in the periodic table. Key to answers on page 27.Lesson 1. The Periodic Table and the Symbols of Elements This lesson will show you how to read symbols of elements in the periodic table. Itwill also focus on the historical background of the development of the periodic table. What you will do Activity 1.1 Read the history of the development of the periodic table and answer the questionsafter the selection.A. History of the Periodic Table The early years of the 19th century witnessed a rapid development in chemistry. Theart of distinguishing similarities and differences among atoms prompted scientists to devisea way of arranging the elements. Relationships were discerned more readily among thecompounds than among the elements; thus, the classification of elements lagged manyyears behind the classification of compounds. In fact, no general agreement had beenreached among chemists as to the classification of elements for nearly half a century afterthe systems of classification of compounds had been established. It was in 1817 when Johann Wolfgang Döbereiner showed that the atomic weightof strontium lies midway between those of calcium and barium. Some years later he showedthat other such “triads” exist (chlorine, bromine, and iodine [halogens] and lithium, sodium,and potassium [alkali metals]). He also showed that similar relationships extended furtherthan the triads of elements, fluorine being added to the halogens, and magnesium to the -4-

alkaline-earth metals. Oxygen, sulfur, selenium, and tellurium were classed as one family,and nitrogen, phosphorus, arsenic, antimony, and bismuth as another family of elements. Attempts were later made to show that the atomic weights of the elements could beexpressed by an arithmetic function. In 1863, A.E.B, De Chancourtois proposed aclassification of the elements based on the new values of atomic weights given by StanislaoCannizzaro's system of 1858. De Chancourtois plotted the atomic weights on the surface ofa cylinder with a circumference of 16 units, corresponding to the approximate atomic weightof oxygen. The resulting helical curve brought closely related elements onto correspondingpoints above or below one another on the cylinder, and he suggested in consequence that“the properties of the elements are the properties of numbers,” a remarkable prediction inthe light of modern knowledge. Another way of classifying the elements was later proposed by John AlexanderReina Newlands in 1864. He proposed that elements be classified in the order ofincreasing atomic weights, the elements being assigned ordinal numbers from one upwardand divided into seven groups, with each group having properties closely related to the firstseven of the elements then known: hydrogen, lithium, beryllium, boron, carbon, nitrogen,and oxygen. This relationship was termed the law of octaves, by analogy with the sevenintervals of the musical scale. As a result of an extensive correlation of the properties and the atomic weights of theelements in 1869, Dmitri Inovich Mendeleev proposed the periodic law, which states that“the elements arranged according to the magnitude of atomic masses show a periodicchange of properties.” Lothar Meyer had independently reached a similar conclusion,published after the appearance of Mendeleev's paper. He wrote down the properties andatomic weights of the elements on cards. There were only 63 elements known at the time.He arranged and rearranged the cards in columns. Eventually he realized that there was arepeating (or periodic) relationship between the properties of the elements and their atomicweights. When the elements are arranged in order of increasing atomic weights theproperties of the elements were repeated very often. He understood the importance of thisdiscovery. What you will do Selt-Test 1.1Fill in the blanks with the word / words that best complete(s) the statements below:1. The first scientist who arranged the elements into group of threes with the same properties was ___________.2. The arrangement of grouping elements by three’s is called ______________.3. Elements were also grouped by eight. This was devised by __________________. -5-

4. Arranging the elements into groups of eight was termed as the Law of _____________.5. The modern periodic table was devised by ___________. Key to answers on page 27. What you will do Activity 1.2 Below is Mendeleev’s version of the periodic table: The rows 1 to 7 are called periods. The columns I A on the left to 0 on the right areknown as groups. Elements with similar properties fall into vertical columns (groups) andhorizontal rows (periods), which form the table. Elements within the groups have similarvalences. Mendeleev left spaces in his table for elements not yet discovered. He alsopredicted what properties these undiscovered elements would have. Between 1875 and1886, the elements gallium, scandium and germanium were discovered. They all fitted intothe positions predicted by Mendeleev. As a result, the periodic law gained universalacceptance. The elements in the same row have something in common. All of the elements in aperiod have the same number of electron shells. Both elements in the top row (the firstperiod) have one shell for their electrons. All elements in the second period have twoelectron shells. The number of shells increases as you go down the table. The columns in the table are called Groups. The elements in a group have the samenumber of electrons in their outer shell. So, all elements in Group I have one electron intheir outer shells. The elements in Group II have two electrons in the outer shell. -6-

Figure 1. Mendeleev’s Version of the Periodic TableBased from the periodic table of Mendeleev, below is the modern version: Atomic mass -7-

Study the terms below for you to be familiar with the modern periodic table: periodic table - The periodic table is a chart of all the known elements in order of increasing atomic number. The table puts elements into groups with similar characteristics, allowing us to recognize trends over the whole array of elements. atom - An atom is the smallest unit of a substance that still has all the properties of that substance. In most cases, an atom consists of protons, neutrons, and electrons. The protons and neutrons are found in the center of the atom, called the atomic nucleus, and the electrons orbit or circle around the center of the nucleus in paths called orbitals. atomic number - The atomic number of an atom is equal to the number of protons that the atom contains. Atoms can have differing numbers of neutrons and electrons while still retaining the original characteristic properties of that atom. However, if an atom gains or loses a proton, in essence, it changes its atomic number and becomes an entirely new atom with new characteristics. atomic weight/mass - The atomic weight of an atom is a measure of how much mass an atom has. The atomic weight is calculated by adding the number of protons and neutrons together. Atomic masses are not listed as whole numbers on the periodic table because atoms can come in forms with different amounts of neutrons. The atomic weight reported for any particular element is an average weight of all the known forms of that element.The Elements in the Periodic TableA. How are elements named? Chemists have developed a unique system of symbols and notation designed tosimplify the writing of chemical symbols, formula, and reactions. This system also showsthe mathematical relations of atoms and reacting chemicals, the way atoms are put togetherto form complex molecules, and the type of chemical bond between atoms. The early alchemists used various symbols to represent the 92 natural elements theyused, a custom that was continued into the 19th century. Jacob Berzelius of Sweden wasthe first to use letters to represent the elements. In most cases he was able to use the firstletter of the name of the element as its symbol; O stood for oxygen, C for carbon, H forhydrogen, and so on. Two letters are used to distinguish between elements that have thesame initial letter, e.g. N for nitrogen, Ne for neon, and Ni for nickel. Sometimes thesymbol is derived from the Latin name of the element, e.g. gold (aurum) is Au, iron(ferrum) is Fe, and lead (plumbum) is Pb. Whenever two letters are used for an element,the first letter is capitalized but the second is not. Thus the element cobalt, Co, isdistinguished from the compound carbon monoxide, CO. -8-

Because of continued search for synthetic elements, aside from the 92 naturally -occurring elements there are man-made elements which were named by scientists asfollows. Element Familiar Place or Name Symbol of ElementCalifornium CaliforniaEinsteinium Albert Einstein CfNobelium Alfred Nobel (Nobel Prize) EsNeptunium Neptune NoPlutonium Pluto NeAmericium America PuBerkelium Berkeley, California AmCurium Marie and Pierre Curie BkFrancium France CuScandium Scandinavia FrPolonium Poland ScTungsten Wolfrom (Peter Woulf) Po W These elements are organized using the periodic table. (Please refer to the modernversion of the periodic table in inset.) A periodic table is a classification and tabulation ofthe elements in the order of their atomic numbers and atomic masses that show theelements' chemical and physical properties.B. How are elements grouped? Take note of the color-coding in the periodic table. Elements are grouped accordingto metals, nonmetals and metalloids. Metals are solid, malleable, ductile and goodconductors of heat. They also possess luster. The only liquid metal is mercury, (Hg).Nonmetals can be solids, liquids or gases. The only liquid nonmetal is bromine, (Br). Inbetween metals and nonmetals that lie along either side of the zigzag line of the periodictable are the metalloids. Some of these elements like boron (B) and silicon (Si) are usedas semiconductors.C. How are elements classified?Elements are classified based on their positions or locations in the periodic table.Group I A - The Alkali MetalsGroup 1 elements are soft silvery metals. They react strongly with water. The furtherdown the group you go, the more violent this reaction is. These alkali metals areusually stored under oil to protect them from moisture and oxygen. They all have oneelectron in their outer shells. In a chemical reaction an alkali metal atom loses thissingle electron. It achieves the stable electron structure of the noble gases. -9-

Group II A – The Alkaline Earth Metals This group consists of all metals that occur naturally in compound form. They are obtained from mineral ores and form alkaline solutions. These are less reactive than alkali metals. Group III A – The Aluminum Group The elements in this group are fairly reactive. The group is composed of four metals and one metalloid which is boron. Group IV A – The Carbon Group This group is composed of elements having varied properties because their metallic property increases from top to bottom meaning the top line, which is carbon, is a nonmetal while silicon and germanium are metalloids, and tin and lead are metals. Group V A – The Nitrogen Group Like the elements in group IV A, this group also consists of metals, nonmetal and metalloids. Group VI A – The Oxygen Group This group is called the oxygen group since oxygen is the top line element. It is composed of three nonmetals, namely, oxygen, sulfur and selenium, one metalloid, (tellurium) and one metal (polonium) Group VII A – The Halogens This group is composed of entirely nonmetals. The term “halogens” comes from the Greek word hals which means salt and genes which means forming. Halogens group are called “salt formers”. Group VIII A – The Noble Gases This group is composed of stable gases otherwise known as the non-reactive or inert elements. The transition elements The elements in the middle of the table are called transition elements. They are all metals and so they are also called transition metals. The system of grouping elements over A and B groups was devised by theInternational Union of Applied and Pure Chemistry (IUPAC) to eliminate confusion. - 10 -

Lesson 2. Properties of Elements in the Periodic Table This lesson will focus on the arrangement of the elements in the periodic table basedon their properties. What you will do Activity 2.1 Read the comic strips below. You will need your own periodic table for this activity: How are elements Take note ofarranged in the periodic the propertiestable? Elements are as you go toarranged from the lightest the right and asto heaviest.…. you go down. ….. and elementsin the same column havematching properties. Why is it so? The properties of elements in the group appear to be periodic. - 11 -

Ah, OK! I don't mean to pick on you. What you said was actually a very important insight. The periodic table is full of repeating patterns. Take atomic size, for instance: atoms get bigger as you move down a column, and smaller as you move to the right across a row, or period.Study the table below.What does it show?Compare it to yourown periodic table. - 12 -

Now, I know. That's so weird! IThe atomic size thought atoms gotbecomes smaller as I bigger as they gotgo from left to right, heavier; why do theyand becomes bigger get smaller as youas I go from top to move to the right?bottom. OK! What about its atomic structure? That’s another thing. We’ll talk about that when we go to the next lesson. For the mean time, let’s summarize what you’ve learned in this lesson.Two distinct trends are noticeable in theatomic size or atomic radius of theperiodic table: 1. Atoms get larger going down a group (vertical arrangement or colum- n13); -and 2. Atoms get smaller moving from left to right across each period (horizontal arrangement of elements).

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