Chemistry Matters for G.C.E. ‘O’ Level Chapter 6

Chapter 6 Ionic Bonding

Answers to Textbook Exercises

Quick Check (page 90)

Charge on the ion = 12 – 10 = +2The ion is magnesium ion, Mg2+. [Mg atom = (2, 8, 2); Mg ion = (2, 8)]

Test Yourself 6.1 (page 92)

1.Ion Number

of protons

Number of

neutrons

Number of

electronsH+ 1 0 0

Be2+ 4 5 2F 9 10 10

2. Charge is –3, ion is N3–.

3. Copper(I) oxide: Cu+, O2–. Copper(II) sulphate: Cu2+, SO42–

Test Yourself 6.2 (page 96)

1. Sodium and bromine, NaBrIron and bromine, FeBr2 or FeBr3

Sodium and sulphur, Na2SIron and sulphur FeS or Fe2S3

2. Sodium oxide: Na2O Aluminium nitrate: Al(NO3)3 Calcium hydroxide: Ca(OH)2 Potassium sulphate: K2SO4 Calcium sulphate: CaSO4

Test Yourself 6.3 (page 99)

1. (a) Strontium chloride is an ionic compound. The ionic bonding between Sr2+ and Cl– is very strong and a lot of energy is needed to break the bond.

(b) It is insoluble in organic solvents and conducts electricity when dissolved in water.

2. Magnesium oxide is an ionic compound. It has a high melting point and thus can withstand high temperatures inside the furnace.

3. Each positive ion M2+ is placed next to a negative ion X2–. The ratio of M2+ ions to X2–

ions is 1:1. Hence, the chemical formula of the ionic compound is MX.

Exercise 6 (page 100)

Foundation

1. A 2. B 3. D 4. D

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Chemistry Matters for G.C.E. ‘O’ Level Chapter 6

5. He, Li+, H– and Be2+ (any three)

6. Ionic compounds have high melting and boiling points and are non-volatile. Hence, they cannot be used to make perfumes. They are solids at room temperature.

7. (a) 27 (b)

(c) Y2O3

Challenge

1. D 2. B

3. (a) (i) Solid. Ionic compounds have high melting points. (ii) Metal. A metal and non-metal (bromine) react to form an ionic compound. (b) It is soluble in water, but not in organic solvents. It conducts electricity in the

molten and aqueous states. (c) +2 (d) XO

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13p, 14n