Write in brief on
(ii) interstitial hydrides.

Explanation

Interstitial hydrides : These are formed by many of d- and f- block elements. But metals of 7,8 and 9 groups do not form hydride. This part of the periodic table is called hydride gap. These are non-stoichometric compounds. Eariler it was thought the hydrogen atoms occupy the interstitial voids of metal crystals. So they are as interstitial compounds. This is correct only in the case of Ni, Pd, Ce and Ac. In most of other cases the crystal structure of metals is changing during the formation of these hydrides.
Some metals like Pd and Pt absorb large amounts of hydrogen. This property is known as occlusion. This property is known as occlusion. This property is also used as a storage of `H_(2)` and purification of `H_(2)`. Also used in catalytic reduction`//`hydrogenation reactions.