Central atoms with more than 8 electrons

[Cameron_Greenberg_3C]

How can you tell when a central atom is allowed to have more electrons than the octet? I know the extra electrons go to the d-orbital, but it seems like some of the given atoms like P and S are in period three and have no d-orbital? It just seems a bit random as to when to put 5 or even 6 bonds.

[Emma Scholes 1L]

Any atom that is in the third period or below can have an expanded octet.

[Tam To 1B]

Elements such as P or S do have open d-orbitals. This is because they have 3s and 3p orbitals already and have available 3d orbitals that can be filled next, allowing them to break the octet rule and have expanded valence shells. On the other hand, this wouldn't work for elements before period 3, because there are no d orbitals on previous energy levels.
A way you can check the amount of extra bonds to put is to calculate formal charge of the central atom. It should be 0 or greater; not a negative number.

[Courtney McHargue 1I]

Any element in the third period or below can have an expanded octet with more than 8 valence electrons. They do have a d-orbital and are large enough to stably hold more electrons in their shells. But, if you have more that 8 electrons in your lewis structure for a certain molecule, try to make sure that its formal charge is 0 to get the most stable structure.