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 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

(b)

Quick Check (page 80)

Number of protons = number of electrons = 2 + 8 + 4 = 14Number of neutrons = 28 – 14 = 14

Test Yourself 5.2 (page 82)

1. The electronic configuration of Al 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

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Chemistry Matters for G.C.E. ‘O’ Level Chapter 5

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Chemistry Matters for G.C.E. ‘O’ Level Chapter 5

5. Element Lithium ChlorineProton number 3 17Nucleon number 7 35Electrons in one atom

3 17

Protons in one atom 3 17Neutrons in one atom

4 18

6. (a) nucleus; protons; neutrons (b)

Particles in gold

Relative charge

Relative mass

Proton +1 1Neutron 0 1Electron –1

7. (a) Atoms of the same element with the same number of protons but different number of neutrons.

(b)

Per atomIsotope

Carbon-12 Carbon-14Number of protons

6 6

Number of electrons

6 6

Number of neutrons

6 8

8. (a) They have the same number of protons, electrons and electronic configurations. (b) O-16 has 8 neutrons. O-17 has 9 neutrons.

9. (a)(i) 2 (ii) 4 (iii)

(b)(i)

(ii) 2, 6

Challenge

1. (a)

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2p1n

ee

e

e8p8n

e

ee

ee

e

Chemistry Matters for G.C.E. ‘O’ Level Chapter 5

Type of atom

Relative percentage present 51.4% 48.6%Protons in one atom 47 47Electrons in one atom 47 47Neutrons in one atom 60 62

(b) Isotopes

2. (a)(i)

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

Critical Thinking (page 86)

1. (i) 8 protons and 8 neutrons

(ii)

2. Proton has a mass of 1 unit and a charge of +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) 9 protons and 10 neutrons

(ii)

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