Ionic Bonding

6 marks · Normal

This question is about the bonding and formulae of calcium chloride and other ionic compounds.

(a)

Draw a dot-and-cross diagram to show the ionic bonding in calcium chloride ().

[3 marks]

(b)

State the electronic configuration of a chloride ion.

[1 mark]

(c)

Write the formula for copper(II) nitrate.

[2 marks]

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(a) Dot-and-cross diagram shows 1 Ca2+ ion, 2 Cl− ions; full electron transfer; ions with correct charges. · must show Ca2+ ion (empty outer shell), two Cl− ions (full outer shell [2,8,8]), two electrons transferred

(b) 2,8,8 · must show 2,8,8

Common mistakes: incorrect arrangement in diagram (not showing both chloride ions); wrong number of electrons in electronic configuration; missing brackets on nitrate group formula

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Positions and charges of ions correctly shown (1 Ca2+, 2 Cl−).

B2 (a) · 1 mark · Electron transfer clearly indicated (from Ca to each Cl).

B3 (a) · 1 mark · Full electronic structure of ions (Cl−: 8 outer electrons).

B4 (b) · 1 mark · Correct electronic configuration for Cl−: 2,8,8.

B5 (c) · 2 marks · Formula for copper(II) nitrate correctly written as Cu(NO3)2.

Worked solution

a) Calcium atom (2,8,8,2) loses two electrons to become Ca2+ (2,8,8). Each electron is gained by a different chlorine atom (2,8,7 each) to form two Cl− ions (2,8,8 each). Diagram shows Ca2+ ion (no outer electrons), two Cl− ions (each with 8 outer electrons), and movement of 1 electron to each Cl atom.

b) Chloride ion, Cl−, has gained 1 electron. Its electronic configuration is 2,8,8.

c) Copper(II) is Cu2+; nitrate is NO3−. To balance the charges, need two nitrate ions per copper(II) ion. Formula: Cu(NO3)2.