What is the reason behind the blue colouration of alkali metals with liquid ammonia?
`M+(x+y)NH_(3)to[M(NH_(3))_(x)]^(+)+[e(NH_(3))_(y)]^(-)`

Explanation

The blue colour of the solution is due to the ammoniated electron which absorbs energy in the visible region of light and thus imparts blue colour to the solution. The solutions are paramagnetic and on standing slowly liberate hydrogen resulting in the formation of amide. In concentrated solution, the blue colour changes to bronze colour and become diamagnetic.