Exceptions to the Octet Rule Question

[Bita Ghanei 1F]

Do P, S, and Cl ALWAYS have to defy the octet rule? Is it only if they are the center atom in the lewis dot structure?

Thanks in advance!

[AVerma_F19]

I believe that they generally do. To have an FC of 0, they need an expanded octet.

[SMIYAZAKI_1B]

In general senses, those elements will be an exception to the octet rules. Of course it does not mean that they HAVE to always, but in most of the cases, it is much more stabilized if they defy the octet rule due to formal charges being close to 0. If you recall like HClO4, you know that formal charge will be less if three of the oxygens have the double bonds in comparison to single bonds.

[andrewcj 2C]

They do not always violate the octet rule. A simple counterexample would be HCl, which follows the rule.