Explain why `BeH_(2)` molecule has a zero dipole moment although the Be - H bonds are polar.

Explanation

The Lewis structure for `BeH_(2)` molecule is as follows: H : Be : H
There is no lone pair at the central atom (Be) and there are two bond pairs. Hence, `BeH_(2)` is of the type `AB_(2).` It has a linear structure.

Dipole moments of each Be--H bond are equal and opposite in direction. Therefore, they nullify each other. Hence, `BeH_(2)` has a net zero dipole moment.