How does ammonia react with a solution of `Cu^(2+)`?

Explanation

`Cu^(2+)` ions react with excess of ammonia to form a deep blue coloured complex.
`Cu^(2+)(aq)+4NH_(4)OH(aq)tounderset("Tetramminecopper (II) ion (Deep blue)")([Cu(NH_(3))_(4)]^(2+))+4H_(2)O`