Question

Explain why \(BeH_2\) molecule has a zero dipole moment although the \(Be-H\) bonds are polar

Answer 1

Concept Used:

Dipole moment of a molecule depends on both the polarity of bonds and the molecular geometry.

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Explanation:

In the BeH₂ molecule, each Be–H bond is polar because beryllium and hydrogen have different electronegativities.

However, BeH₂ has a linear geometry with a bond angle of 180°.

The two Be–H bond dipoles are equal in magnitude but act in opposite directions along the same straight line.

As a result, the dipole moments of the two Be–H bonds cancel each other.

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Conclusion:

Although the Be–H bonds are polar, the BeH₂ molecule has zero dipole moment due to its symmetrical linear structure.

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Final Answer:

BeH₂ has zero dipole moment because the equal and opposite dipole moments of the polar Be–H bonds cancel each other.