Question

Would the bromate ion have C3v point group due to the trigonal pyramidal geometry? I see a C3 rotational axis and a vertical plane of symmetry. Am I missing anything in terms of the double bonds or are those the only symmetry operations in this molecule?

Answer 1

The bromate ion has a trigonal pyramidal shape and does not have a C3v point group due to the presence of a lone pair of electrons on the central atom, which reduces its symmetry.

Step-by-step explanation:

The question is whether the bromate ion would have a C3v point group due to its trigonal pyramidal geometry. The bromate ion does contain a central bromine atom surrounded by three oxygen atoms in a trigonal pyramidal arrangement, which includes a single lone pair of electrons on the bromine.

This does indeed give the molecule a single C3 axis of rotation. However, it's important to note that the presence of a lone pair breaks the vertical symmetry plane that would be required for a molecule to have a C3v point group.

Instead, the bromate ion has a molecular geometry similar to that of a trigonal pyramid, which reduces its symmetry compared to a trigonal planar species like BCl3 which has no lone pair and belongs to the C3v point group.