Ionic bonding in magnesium oxide
3 marks · NormalExplain how magnesium and oxygen atoms form ions when magnesium reacts with oxygen. Include reference to electrons and charges.
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Magnesium loses 2 electrons to form Mg^{2+}; oxygen gains 2 electrons to form O^{2-}
Also accept: Mg atom loses two electrons to become Mg^{2+} (cation); O atom gains two electrons to become O^{2-} (anion)
Common mistakes: Magnesium gains electrons; Oxygen loses electrons
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Marking points
M1 · 1 mark · Says magnesium atom loses two electrons
A1 · 1 mark · Gives correct charge: Mg^{2+}
M2 · 1 mark · Says oxygen atom gains two electrons, forming O^{2-}
Worked solution
Magnesium atom loses 2 electrons and becomes a Mg^{2+} ion:
Oxygen atom gains 2 electrons and becomes an O^{2-} ion: