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Why higher energy is required for stretching vibration as compared to the bending vibrantion?

1 Answer
Mar 8, 2018


Here's what I get.


Stretching vibrations

In a stretching vibration, the atoms move in and out along the internuclear axis.


The nuclei are moving apart against the attraction of the bonding electrons between them.

Bending vibrations

In a bending vibration, the bond length does not change.


Instead, the bond angle changes.

The angle distorts from the ideal angle for the orbitals (say, 120° or 109.5°).

It is easier to bend a bond than to stretch it because the nuclei are not moving against the attraction of the bonding electrons.

Thus, a stretching vibration has a higher frequency and requires more energy than a bending vibration.