Chemistry Matters Ch05 Textbk ANS

Chemistry Matters for G.C.E. ‘O’ Level

Chapter 5

Chapter 5

Atomic Structure

Answers to Textbook Exercises Quick Check (page 76) Atomic number of  X  = 30

÷

2 = 15

Test Yourself 5.1 (page 77) 1. A neutron has much more mass than an electron. The The neutron carries no electric charge while the electron carries an electric charge of –1. 2. (a) Number of electrons = 7 electrons Nucleon number = 7 + 7 = 14 14

(b)

 X   7

Quick Check (page 80) Number of protons = number of electrons = 2 + 8 + 4 = 14 Number of neutrons = 28 – 14 = 14

Test Yourself 5.2 (page 82) 1. The electronic electronic configuration configuration of A l is as follows:

Its electronic configuration is (2, 8, 3). 2.

Sodium: (2, 8, 1)

Lithium: (2, 1)

Similarity: They have one valence electron. Difference: Sodium has 3 electron shells but lithium has 2 electron shells.

Exercise 5 (page 84) Foundation 1. B

2. B

3. B

4. C

© Marshall Cavendish International (Singapore) Pte. Ltd.

1

Chemistry Matters for G.C.E. ‘O’ Level

Chapter 5

5. Element Proton number Nucleon number Electrons in one atom Protons in one atom Neutrons in one atom

Lithium 3 7 3 3 4

6. (a) nucleus; protons; neutrons (b) Particles in Relative gold charge +1 Proton

Chlorine 17 35 17 17 18

Relative mass 1

0 –1

Neutron Electron

1 1 1840

7. (a) Atoms of the same element with the same number of protons protons but different number of  neutrons. (b) Isotope Per atom Carbon-12 Carbon-14 6 6 Number of protons Number of electrons 6 6 6 8 Number of neutrons 8. (a) They have the same number of protons, electrons and and electronic configurations. configurations. (b) O-16 has 8 neutrons. O-17 has has 9 neutrons. neutrons. 9. (a)(i) 2 (ii) 4 (iii) 2p 1n

e

e

(b)(i)

e e

e e

8p 8n

e e

e e

(ii) 2, 6

Challenge 1. (a) Type of atom

107 47

Relative percentage present Protons in one atom Electrons in one atom

© Marshall Cavendish International (Singapore) Pte. Ltd.

Ag

51.4% 47 47

2

109

Ag 47

48.6% 47 47

Chemistry Matters for G.C.E. ‘O’ Level

Neutrons in one atom (b) Isotopes

Chapter 5

60

62

3

2. (a)(i)

T 1

(ii) T2O (b)(i) 2 (ii) 2 (iii) 3

Critical Thinking (page 86) 1. (i) (i) (ii)

8 pro proto tons ns and and 8 neut neutro rons ns 1 6

O

8

2. Proton has a mass of 1 unit and a charge charge of +1. +1. Electrons have negligible mass and a charge of –1. If these are added together, it produces a mass of 1 unit with no charge i.e. a neutron. 3. (i) (i) (ii)

9 pro proto tons ns and and 10 10 neu neutr tron onss 1 9

Y  

9

© Marshall Cavendish International (Singapore) Pte. Ltd.

3