Give reasons for the following: (a) Na, K and Ca metals form hydride by combination with hydrogen gas, but most other metals do not

Give reasons for the following:
(a) Na, K and Ca metals form hydride by combination with hydrogen gas, but most other metals do not.
(b) Aluminium easily combines with oxygen but, still it can be used for making kitchen utensils.
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(a) Metals like Na, K and Ca can force the hydrogen atoms to accept electron given by them and form hydrides.

(b) Aluminium though easily combines with oxygen to form aluminium oxide, but the oxide which is formed is protective oxide layer. Hence, used for making utensils.