When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

Explanation

The dilute solutions of alkali metals in liquid ammonia are blue. As the concentration increases, the colour changes to bronze. The blue colour of alkali metals is due to the ammoniated electrons.
`M+(x+y)NH_3 to [M(NH_3)_x]^(+)[e(NH_3)_y]^(-)`
Alkali metal Ammoniated electron However, when the concentration increases, the ammoniated metal ions may get bound by free electrons and the colour becomes copper bronze. `2e^(-)(NH_3)_y to [e^(-)(NH_3)_y]_2`