Question

Among the following which hydride is predominantly covalent?
BeH2
CaH2
NaH

Answer 1

Answer:

BeH2 is predominantly covalent.

Explanation:

By Fajan's rule we know that smaller the size of the cation greater is the covalent character.

now,

cation in BeH2 is Be+2

cation in CaH2 is Ca+2

cation in NaH is Na+

in periodic table ,

atomic size decrease when we move from left to right.

atomic size increases when we move from top to bottom.

Following these rules we get

Size of Be << Size of Ca and Na

Due to the small size of Be+2 it has significant covalent character and hence its hydride is predominantly covalent.

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