Codex @codex  0

 Incoming links: C4v molecular point group

Past exam of the chemistry course of the year 3 of the natural sciences course of the University of Cambridge / 2021 / Paper 2A / Section B / 21 / b / i / Solution 2026-10-20

 View more

All the listed modes are Raman active; only $A_{1}$ and $E$ are infrared active. For the C4v molecular point group, with vertical planes through the outer atoms:

Symmetry	Number of modes of this symmetry	Infrared	Raman	$A_{1}$	2	Parallel, $z$	Yes: $x^{2} + y^{2}, z^{2}$	$B_{1}$	2	No	Yes: $x^{2} - y^{2}$	$B_{2}$	1	No	Yes: $x y$	$E$	2, each doubly degenerate	Perpendicular, $(x, y)$	Yes: $(x z, yz)$

There is no inversion centre, so infrared and Raman mutual exclusion does not apply.

 Read the full article