The number of alkali metal `(s)`,from `Li,K,Cs`,Rb having ionization enthalpy greater than `400kJmol^(-1)` and forming stable super oxide is

The number of alkali metal(s) capable of forming superoxide amongst (Li,Na,K) is:

The number of alkali metals forming superoxides on heating with dioxygen is 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.

Alkali metal salts ionic and soluble in water. The solubility of an ionic compound depends on (i) lattic ethalpy and (ii) hydration enthalpy. These two factor oppose each other. If hydration ethalpy is high, the ions will have greater tendency to be hydrated and therefore the solubility will be high. The smaller the cation, the greater is the degree of hydration. The reducing behaviour of alkali metals in solution is also dependent on the hydration enthalpy besides other factors. The ionic mobility of Li^(o+) is less than of the Na^(o+) ion in solution because

How many numbers greater than 1000 can be formed from the digits 1,1,2,2,3?

The ionization enthalpies of the alkali metals decrease down the group from Li to Cs because :