The property of hydrides of p–block elements mostly depends on :

(i) electronegativity difference between central atom and hydrogen

(ii) size of central atom

(iii) number of valence electrons in central atom

Some undergo hydrolysis in which central atom is less electronegative, react with OH – to give hydrogen. While acidic property of hydride in a period depends on electronegativity of central atoms, i.e. more electronegative is the atom, more acidic is hydride. Ι n a group, acidic property is proportional to size of central atom. Some electron deficient hydride behaves as Lewis acid while only one hydride of an element in p–block behaves as Lewis base with lone pair of electrons. Hydrides in which central atom’s electronegativity is close to hydrogen has no reaction with water.

(i) Which one is the weakest acid among the following ?