When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution.
`M+(x+y)NH_(3)rarrM^(+)(NH_(3))_(x)+e^(-1)(NH_(3))_(y)`
The ammoniated electrons absorb energy corresponding to red region of visible light. Therefore, the transmitted light is blue in colour.At a higher concentration (3 M), clusters of metal ions are formed. This causes the solution to attain a copper–bronze colour and a characteristic metallic lustre.
