Breaking the Octet Rule

[Gina_Chiarolla_3C]

Are there any situations where the octet rule can be broken where an atom can contain less than 8 elections? Or does the atom have to satisfy the octet rule in all situations? I know there are exceptions for H, He, Li, and Be. But are there situations for any other elements?

[Reem Abu-Shamma 2H]

There are some cases in which an atom can have more than 8 valence electrons. These atoms are known to have an "expanded octet". This happens for some atoms in the third period and for atoms in periods below that. Some common examples are Phosphorous in PCL5 (which has 10 valence electrons) and Sulfur in SF6 (Which has 12 valence electrons).
Hope this helps!

[Josh Ku 3H]

I also believe that Boron and Aluminum can have exceptions to the rule as well. They both can have just 6 electrons instead of the eight.

[Timothy Yu 2M]

Is there a specific reason why these atoms do not follow the octet rule? Is there also a pattern as to figure out which ones these apply to or not?

[Divya Kumar 3I]

I recall Dr.Lavelle saying that elements in period 3 and/or group 13 of the periodic table tend to be exceptions to the octet rule. As such, elements like boron, aluminum, sulfer, and phosphorus tend to be exceptions to the octet rule. I hope that helps!

[DBaquero]

So in general there are a few ways to tell if you might be dealing with an exception to the octet rule. 1.) When you add up all of the valence electrons for the molecule, you get an odd number. So something like nitric oxide (NO) will have 11 electrons, so there isn't any way you can satisfy the octet rule. 2.) Obviously whenever you're dealing with an element that only has the 1s or 2s shell (H,He,Li,Be). 3.) When you're dealing with elements in any p-block from period 3 and on (so like SF6 or PCl5).

[Meera McAdam 1C]

Thanks, that was succinct and helpful.