Question

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

Answer 1

The dilute solution of alkali metals in liquid ammonia exhibit dark blue colour because ammoniated electrons absorb energy corresponding the red region of the visible light .
`M + (x + y) NH_(3) to [M (NH_(3))_(x) ]^(+) + underset("Ammoniated electrons")(e^(-) (NH_(3))_(y))`
However , if the concentration increases above 3M , the colour changes to copper-bronze and the solution acquires metallic lustre due to the formationof metal ion clusters.