its freshly exposed shiny surface rapidly turns dull as a thin layer of sodium oxide forms: Other metals may oxidise more slowly. Gold and other very unreactive metals do not oxidise in air at all.

The shiny grey magnesium strip changes to a white powder called magnesium oxide. Learn more about making a reactivity series in this guide. For example, sodium is burned to make sodium oxide.

Sodium oxide and potassium oxide dissolve in water to produce alkalis: • Na 2 O(s) + H 2 O (l) → 2 NaOH (aq) • K 2 O(s) + H 2 O (l) → 2 KOH (aq) • 2K(s) + 2H 2 O (l) → 2KOH (aq ...