Question

what happens when metals react with oxygen in the air

Answer 1

Reaction with oxygen. Remember that metals react with oxygen in the air to produce metaloxides, like magnesium oxide. Non-metals react with oxygen in the air to produce non-metal oxides. Here are two examples for the non-metals carbon and sulphur.

Answer 2

when metals react with oxygen, the metal atoms tend to lose electrons to the oxygen atoms, changing their oxidation state and characteristically their colour. This is why rust is red, copper can be green or blue and why transition metals can provide us with bright and colourful solutions.