Question

Explain why BeH₂ molecule has a zero dipole moment although the Be–H bonds are polar.

Answer 1

BeH₂is a linear molecular (H-Be-H), the bond angle = 180°.

Be-H bonds are polar due to a difference in their electronegativity but the bond polarities cancel each other. Thus, molecule has resultant dipole moment of zero.

Answer 2

The Lewis structure for BeH₂ is as follows:

There is no lone pair at the central atom (Be) and there are two bond pairs. Hence, BeH₂ is of the type AB₂. It has a linear structure.

Dipole moments of each H–Be bond are equal and are in opposite directions. Therefore, they nullify each other. Hence, BeH₂ molecule has zero dipole moment.