Question
Explain why $\mathrm{BeH}_2$ molecule has a zero dipole moment although the Be–H bonds are polar.
✓
Answer
The Lewis structure for $\mathrm{BeH}_2$ is as follows:
$\text{H}:\text{Be}:\text{H}$
There is no lone pair at the central atom ( Be ) and there are two bond pairs. Hence, $\mathrm{BeH}_2$ is of the type $\mathrm{AB}_2$. 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, $\mathrm{BeH}_2$ molecule has zero dipole moment.
$\text{H}:\text{Be}:\text{H}$
There is no lone pair at the central atom ( Be ) and there are two bond pairs. Hence, $\mathrm{BeH}_2$ is of the type $\mathrm{AB}_2$. 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, $\mathrm{BeH}_2$ molecule has zero dipole moment.
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