Giant ionic structures

2 marks · Easy

Potassium oxide (K_2O) is an ionic compound formed from K^+ and O^{2-} ions.

Calculate the total positive charge provided by the potassium ions in one formula unit of potassium oxide.

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+2 charge units (or +2) (±0)

Must show: 2 × K^+ ions

Also accept: 2

Common mistakes: 1; +1

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Marking points

M1 · 1 mark · Identifies there are two potassium ions in K_2O or works out 2 × (+1)

A1 · 1 mark · Calculates total positive charge as +2

Worked solution

Each potassium ion is K^+ (+1 charge).

There are 2 potassium ions in K_2O.