202110243-TRIUMPH-STUDENT-WORKBOOK-PHYSICAL_SCIENCE-G09-PART1

A. Rutherford stated that the electrons are not stationary. They are revolving around the nucleus. The movement of the electrons around the nucleus can be compared to the revolution of planets around the sun, so Rutherford’s model of an atom can be called “Planetary Model”. 2.6 Higher Order Thinking Skills Q1. [AS6] Explain the efforts made by scientists to explain the structure of atom by develop- ing various atomic models? [Refer to TB page 165 Q2] A. • The efforts made by scientists are appreciable and they led to the latest knowledge of the tiny particle atom which is the basic unit of matter. • It has disproved the notion of Dalton that atoms are indivisible. • It leads to the important conclusion that the atoms are electrically neutral. • It leads to the further research on atoms and their behavior and how the chemical prop- erties of elements and compounds vary due to the arrangement of sub atomic particles in an atom. SESSION 2. STRUCTURE OF AN ATOM 299

2.7 Suggested Projects Q1. [AS4] Write a report on the history of unveiling the structure of atom from John Dalton to Neils Bohr. [Refer to TB page 165 Q1] A. Students’ activity. “History of Atom” My name is Miss Atom. I am in the hearts of every particle of matter and owed by all. At first Dalton proposed that I am indivisible. But J.J. Thomson started to study me by his discovery of electrons. It was Earnest Rutherford who introduced the concept of nucleus and divided my character into two parts, namely the nucleus and extra nuclear portion. He said the nucleus contains protons while electrons are present in extra nu- clear part. During the course of my life another scientist James Chadwick said I have another body part called neutron. But the whole structure of my body has been almost explained by Neils Bohr. He said I am electrically neutral as the number of protons is equal to the number of electrons. Neils Bohr postulated that the electrons are revolving around the nucleus in fixed circu- lar paths called energy levels or shells or orbits. The various energy levels are arranged in order of increasing energy starting from my nucleus. The energy of an electron in me has been quantized. He also said that when an electron jumps from higher energy level to lower energy level, it loses energy. My story doesn’t end here. Another scientist Sommerfeld introduced elliptical paths instead of circular paths. My story may be a never ending one because who knowswhen another scientist may strive and put forth another theory to describe me. Objective Questions (1) Which model of atom is known as Planetary Model? ( Pg 165; Q 5) (A) Thomson’s (B) Rutherford’s (C) Bohr’s (D) Modern atomic model Correct Answer: B SESSION 2. STRUCTURE OF AN ATOM 300

SESSION 3 VALENCY, ATOMIC NUMBER, ATOMIC MASS NUMBER, SYMBOLS AND ISOTOPES 3.1 Mind Map 3.2 Terminology i. Valency – Valency is the combining capacity of an atom. ii. Isotopes – Atoms which have the same number of protons but different number of neutrons. 3.3 Key Concepts i. Valency: Combining capacity of atom. ii. The atomic number of an element is the same as the number of protons in the nucleus of its atom. iii. The mass number of an atom is equal to the number of nucleons in its nucleus. iv. Isotopes: Atoms which have the same number of protons but different number of neutrons. 3.4 Reflection on Concepts SESSION 3. VALENCY, ATOMIC NUMBER, ATOMIC MASS NUMBER, SYM... 301

Q1. [AS1] State the valencies of magnesium and sodium. [Refer to TB page 164 Q4] A. Valency of magnesium is 2 and sodium is 1. 3.5 Application of Concepts Q1. [AS1] Define valency by taking examples of nitrogen and boron. [Refer to TB page 164 Q3] A. Valency: The combining capacity of an atom is called valency. Valency of nitrogen: Atomic number of nitrogen is 7. Electronic configuration is 2, 5. But it is easier, for nitrogen to gain 3 electrons to have its ‘L’ shell filled with 8 electrons rather than to lose 5 electrons. So, valency of nitrogen is determined by subtracting 5 from 8 which gives 8–5 = 3 Valency of nitrogen is 3. Valency of Boron: Its atomic number is 5. Electronic configuration is 2, 3. The number of electrons in its valence shell is 3. Valency of Boron is 3. Q2. [AS1] What is the main difference between isotopes of the same element? [Refer to TB page 164 Q4] A. i. Isotopes are atoms of the same element with the same atomic number (Z), but differing in mass numbers due to a difference in number of neutrons. ii. As such the isotopes of the same element differ only in their number of neutrons. iii. Example: Isotopes of carbon:12 C, 14 C Q3. [AS2] If Z=5, what would be the valency of the element? [Refer to TB page 164 Q5] A. If Z=5, the electronic configuration of the element is 2, 3. SESSION 3. VALENCY, ATOMIC NUMBER, ATOMIC MASS NUMBER, SYM... 302

Since there are 3 unpaired electrons in the outer shell, the valency of the element is 3. Q4. [AS4] Fill the missing information in the following table. [Refer to TB page 164 Q6] A. Name Atomic Mass Number Number Symbol Number Num- of of elec- ber neutrons trons Oxygen 16O8 8 16 8 8 Sulphur 34S 16 16 34 18 16 Nitrogen 14N7 7 14 7 7 Beryllium 9Be4 4 95 4 Magnesium 24Mg12 12 24 12 12 Magnesium 25Mg12 12 25 13 12 3.6 Higher Order Thinking Skills Q1. [AS1] Cl- has completely filled K,L & M shells. Explain it on the basis of Bohr–Bury Theory. [Refer to TB page 165 Q1] A. 1. The atomic number of chlorine (Cl) is 17. 2. That is a neutral atom of chlorine contains 17 protons and 17 electrons each. 3. The electronic configuration or distribution of electrons in Cl - is as follows: KLMN 28 8 – SESSION 3. VALENCY, ATOMIC NUMBER, ATOMIC MASS NUMBER, SYM... 303

4. As per the formula 2n2, K shell can hold a maximum of 2 electrons and the L shell 8 electrons. Out of the 17 electrons K and L shells are completely filled with 2 and 8 electrons leaving 7 electrons to enter the ‘M’ shell. Atomic number of chlorine is 17 but Cl - has one more electron compared to Cl atom. 5. So, K and L shells are completely filled with electrons. Objective Questions (1) Valency of Aluminium is (Pg 165; Q 6) (A) 1 (B) 2 (C) 3 (D) 4 Correct Answer: C (2) The gas which is stable without octet configuration is (Pg 165, Q 7) (A) Neon (B) Argon (C) Radon (D) Helium Correct Answer: D (3) The sum of the number of protons and neutrons in an atom is known as its (Pg 165; Q 8) (A) Mass number (B) Atomic number (C) Valency (D) Ion number Correct Answer: A (4) Deuterium and Tritium are the Isotopes of (Pg 165; Q 9) (A) Nitrogen (B) Oxygen (C) Hydrogen (D) Helium Correct Answer: C (5) The electronic configuration of Sodium is (Pg 165; Q 10) (A) 2,8 (B) 8, 2,1 (C)2, 1, 8 (D)2, 8, 1 Correct Answer: D SESSION 3. VALENCY, ATOMIC NUMBER, ATOMIC MASS NUMBER, SYM... 304

—— CCE Based Practice Questions —— AS1-Conceptual Understanding Very Short Answer Type Questions 1. Fill in the blanks. [Refer to Session 9.1 ] (i) The subatomic particle with least mass is __________________ . (ii) A proton is about times heavier than an electron. (iii) The charge of a proton is taken as 1 unit . (iv) Neutron was discovered by . (v) Electron was discovered by . 2. Fill in the blanks. [Refer to Session 9.3 ] (i) Atomic number is the number of present in the of an atom. (ii) and show multiple valencies. (iii) The electrons present in the outermost shell of an atom are called . (iv) The N shell can accommodate a maximum of electrons. (v) gases have 8 electrons in the outermost shell. CHAPTER 9. WHAT IS INSIDE THE ATOM? 305

Long Answer Type Questions 3. Answer the following questions in 6-8 sentences. (i) [(Session 9.1)] Write in brief about protons, neutrons and electrons. 4. Answer the following questions in 6-8 sentences. (i) [(Session 9.2)] Describe Bohr’s model of the atom. CHAPTER 9. WHAT IS INSIDE THE ATOM? 306

5. Answer the following questions in 6-8 sentences. (i) [(Session 9.3)] Summarize the rules for writing the distribution of electrons in various shells for the first 18 elements. AS2-Asking questions and making hypothesis Long Answer Type Questions 6. Answer the following questions in 6-8 sentences. (i) [(Session 9.1)] Imagine what would have happened if Rutherford had performed his experiment using a beam of electrons, instead of alpha particles. How would his observations have differed? What conclusions would he have drawn? CHAPTER 9. WHAT IS INSIDE THE ATOM? 307

AS3-Experimentation and field investigation Long Answer Type Questions 7. Answer the following questions in 6-8 sentences. (i) [(Session 9.1)] Explain Rutherford’s alpha ray scattering experiment. Describe how Rutherford could explain his model of atom based on his observations. CHAPTER 9. WHAT IS INSIDE THE ATOM? 308

AS4-Information skills and projects Long Answer Type Questions 8. Answer the following questions in 6-8 sentences. (i) [(Session 9.2)] The description of atomic particles of two elements X and Y is given below: Atomic particles XY Protons 88 Neutrons 89 Electrons 88 a. What is the atomic number of Y? b. What is the mass number of X? c. What is the relation between X and Y? d. Which element/elements do they represent? e. Write the electronic configuration of X. AS5-Communication through drawing and model making Long Answer Type Questions 9. Answer the following question. (i) [(Session 9.3)] Give the schematic atomic structure of the first 12 elements from hy- drogen to magnesium representing electrons. CHAPTER 9. WHAT IS INSIDE THE ATOM? 309

CHAPTER 9. WHAT IS INSIDE THE ATOM? 310

AS6-Appreciation and aesthetic sense, Values Short Answer Type Questions 10. Answer the following questions in 3-4 sentences. (i) [(Session 9.2)] Why do you appreciate the Bohr’s atomic model? AS7-Application to daily life, concern to bio diversity Long Answer Type Questions 11. Answer the following questions in 6-8 sentences. (i) [(Session 9.3)] What are isotopes? What are the applications of isotopes? CHAPTER 9. WHAT IS INSIDE THE ATOM? 311

Objective Questions AS1-Conceptual Understanding 12. Choose the correct answer. (B) 2 (i) What is the valency of sodium metal? (D) 3 (A) 4 (C) 1 (B) alpha rays (D) none (ii) Positive charge is carried by . (A) beta rays (C)gamma rays (iii) Number of valence electrons in chloride ion is (A) 16 (B) 18 (C) 8 (D) 17 (iv) Atoms form ions when (A) number of proton changes (B) number of electron changes (C)number of neutrons changes (D)number of electrons and protons changes (v) The subatomic particle whose number is not same in two isotopic species of an element is (A) neutrons (B) alpha particles (C) protons (D) electrons (vi) The extra nuclear part of the atom in which electrons revolve are called (A) orbits (B) orbitals (C)energy levels (D)both A and C CHAPTER 9. WHAT IS INSIDE THE ATOM? 312

(vii) The maximum number of electrons that the L shell can accommodate is (A) 2 (B) 8 (C) 18 (D) 16 AS2-Asking questions and making hypothesis 13. Choose the correct answer. (i) The mass of an atom depends on the (A) number of electrons its nucleus contains (B) number of protons its nucleus contains (C)number of protons and neutrons its nucleus contains (D)number of neutrons its nucleus contains (ii) Which one of the following is the correct electronic configuration of sodium? (A) 2,8 (B) 8,2,1 (C) 2,1,8 (D) 2,8,1 AS3-Experimentation and field investigation 14. Choose the correct answer. (i) Gold foil was used in Rutherford’s scattering experiment because it has (A) high refractive index (B) high density (C)high malleability (D)high ductility AS4-Information skills and projects 15. Choose the correct answer. (i) Calcium has 20 electrons. These occupy K,L,M, and N shells. Which shell or shells is /are incomplete? (A) L, M, N shells (B) M, N shells (C)N shell (D)K, L, M, N shells CHAPTER 9. WHAT IS INSIDE THE ATOM? 313

PROJECT BASED QUESTIONS —— Project Based Questions —— (i) Design an experiment (objective, materials required, procedural steps, expected re- sult and safety concern) to find out if adding energy increases the rate of evap- oration. Make a project report on it. (ii) Make a list of motions that you see around yourself in your daily life and classify them into Linear, Circular and Oscillatory motion. Or Collect information on different types of cars and the time they take to reach 100 km/h from rest. Calculate the acceleration in each case and make a table. Which car has the most acceleration and why? Discuss in your class. (iii) Collect information and pictures from internet on few machinery that work on Newton’s third law of motion and make a scrap book. (iv) Design an experiment to demonstrate the principle of refraction of light rays in water. Also collect images from internet to prepare a scrap book on importance of total internal reflection. (v) Make a project report with family members’ assistance to discover substances at home that do or do not dissolve in water. Will various substances dissolve in water once shaken? ((Applying your previous knowledge make a report predicting what will happen when you dissolve (each separately) vinegar, sugar, oil, salt, sand, alcohol, flour, soap, ammonia, and cornstarch in water?)) (vi) So far over a 115 elements have been discovered and known to us . But recently 4 new elements are added in the list. Take help from Newspapers / Science Magazines or internet and make a project report on the discovery of these latest 4 new elements. (vii) The oil brakes in vehicles works on the Pascal's principle. Collect the information on working of air brakes in vehicles and write a report. (viii) When we study about atoms and molecules usually we come across with the names of the great scientists like Antoine Lavoisier, John Dalton, Thomson, Ernest Rutherford, Neils Bohr etc. But there was a Greek philosopher named as DEMOCRITUS who developed one of the first atomist theories of the universe. Take help from your library books or internet and make a project report on Democritus atomic theory. Project Based Questions 314