Question

Bascity of hydride ion than hydroxide ion is better explained by

Answer 1

Superbases are stronger than hydroxide ions and cannot be kept in water; they provide examples of bases that do not contain a hydroxide ion (and are therefore ... amides (NH2–), and hydrides (H–) tend to be even stronger bases due to the .... The base dissociation constant KbE measures a base's basicity, or strength.

In group 15, the hydrides of the formula XH3 have a lone pair on the central atom. As we go down the group, size of the atom increases. And hence, ELECTRON DENSITY OVER THE GROUP 15 ELEMENT DECREASES. That's why the tendency to donate electrons decreases, hence basicity decreases down the group.