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

Only those elements of s-block can produce superoxides which have:-

Alkali metals oxide are obtained by combustion of the metals.Although Na normally gives Na_2O_2 ,it will take up further oxygen at elevated pressure and temperature to form NaO_2 .The per and superoxides of the heavier alkalies can also be prepared by passing stoichiometric amounts of oxygen into their solution in liquid ammonia. The different alkali metal oxides can be distinguished by reaction with water.The superoxides reacts with CO_2 and give oxygen gas.The stability of per and superoxides is based upon that larger cation can stablise larger anion, due to larger lattice energy. Alkali metals dissolve in liquid ammonia.Dilute solutions are dark blue in colour but as the concentration increases above 3M, the colour changes to copper bronze and the solution acquires the metallic lusture due to the formation of metal ions clusters.The solutions of alkali metals in liquid ammonia are good conductors of electricity due to the presence of ammoniated cations and ammoniated electrons.However, the conductivity decreases as the concentrations increases, since ammoniated electrons and ammoniated cation associate. KO_2 is used in oxygen cylinders in space and submarines because it :

Arrange the following elements in the order of the increasing electropositive character. Li, Na, K, Rb, Cs

Total number of element(s) which have only single oxidation state (other than zero) in their corresponding stable compounds: Cs, Ba, F, Zn,Be,Al, Sr,Ga, Pb.