Expanded octet

[Shanzey]

During lecture, Dr. Lavelle mentioned expanded octets, but I am unsure of what he meant by that. What is an expanded octet, and can atoms that follow the octet rule have expanded octets (or is that a violation of the octet rule)?

[FDeCastro_1B]

From what I could gather in lecture, an expanded octet is when a central atom ends up with more than an octet.

[zoedfinch1K]

Expanded octets are when an atom can accommodate more than 8 valence electrons. This only happens for P, S, Cl.

[Harry Zhang 1B]

The expanded octet concept comes from the idea that normally we would consider the valence orbitals of an atom or the outermost shell of an atom can hold no more than 8 electrons. An expanded octet is then an atom that holds more than eight electrons in its outmost shell. Atoms in or after period 3 have the principal quantum number 3, which gives them access to the d orbital. This then allow them to hold extra electrons besides the ones that are already in s(2 electrons) and p(6electrons). However, atoms in group I-III are unlikely to have an expanded octet because they are metal and are thus unlikely to gain extra electrons.