Find the number of s-block elements which can produce ammoniated cation and ammoniated electron with liquid ammonia.

Li, Na, K, Rb, Cs, Ca, Sr, Ba

All can form ammoniated cation and ammoniated electron with liquid ammonia. So the answer would be 8. Alkali metals dissolve in liquid ammonia to produce vivid blue, conductible solutions. This occurs because in an ammonia solution, the valence electron of the alkali metal atom is easily lost.