Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are `Li^(+) lt Na^(+) lt K^(+) lt Rb^(+) lt Cs^(+)`
(b) Lithium is the only alkali metal to form a nitride directly.
(c) `E^(ɵ)" for "M^(2+)`(aq) + 2e `to` m(s) (where M = Ca, Sr or Ba) is nearly constant.