d-Orbitals

[Ariel Fern 2B]

I know that atoms in period 3 or higher can potentially accommodate more than 8 electrons due to the d-orbitals, but is there a sure way to know when the octet rule needs to be exceeded? For instance, in BrF₃, Br exceeds 8 electrons, but in BrO^-, Br follows the octet rule. Is there any way I can be sure that exceeding the octet rule is correct? Thanks!

[505306205]

Usually you can tell if you need the incomplete octet when the number of total electrons doesn't equal the total number of electrons in the structure and you cant accommodate with more bonds.

[Fdonovan 3D]

^^ I agree. Just count the number of electrons that you should have in theory, and then if you end up having extras after all the atoms have their octet then the atom capable of having an expanded octet would get these extra electrons.