bond-angle bending

Bond-angle bending refers to the change in the angle between two chemical bonds that share a common atom. This type of molecular motion is a key aspect of molecular spectroscopy, where it influences the energy states of molecules.1

In molecules, atoms are not static but are in constant vibrational motion. For a diatomic molecule, this vibration involves the oscillation of the bond length around an average internuclear separation. When considering real molecules, these oscillations are anharmonic, meaning the energy levels are not equally spaced and can be perturbed.1

The concept of bond angles is also central to understanding molecular shapes, as described by Valence-Shell Electron-Pair Repulsion (VSEPR) theory. This theory posits that electron pairs around a central atom repel each other, leading to specific geometric arrangements that minimize these repulsions. These arrangements dictate the bond angles within a molecule. For instance, in water (H₂O), the electron pairs around the oxygen atom result in an angular shape with a bond angle of approximately 104°.23