Ionic bonding in magnesium oxide

3 marks · Normal

Explain, using charges, why strong electrostatic attraction exists between the ions in magnesium oxide (MgO), and calculate the charge difference between a Mg^{2+} ion and an O^{2-} ion.

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The Mg^{2+} ion has a 2+ charge and the O^{2-} ion has a 2- charge, so the overall charge difference is 4 units (±0)

Also accept: Charge difference is 4

Common mistakes: Not taking magnitude of charge difference; Saying 0 as difference

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Marking points

M1 · 1 mark · States that Mg^{2+} is positively charged and O^{2-} is negatively charged

M2 · 1 mark · Mentions that electrostatic attraction exists between oppositely charged ions

A1 · 1 mark · Calculates the charge difference: |2 - (-2)| = 4

Worked solution

MgO contains Mg^{2+} ions (2+) and O^{2-} ions (2-), which are oppositely charged.

There is a strong electrostatic attraction between these oppositely charged ions.

The charge difference between Mg^{2+} and O^{2-} is 4 units.