Exceptions to Octet Rule

Moderators: Chem_Mod, Chem_Admin

305115396
Posts: 30
Joined: Fri Sep 28, 2018 12:16 am

Exceptions to Octet Rule

Postby 305115396 » Sun Nov 11, 2018 5:24 pm

What are some exceptions to the octet rule that I should know for sure? Also is it true that basically all elements past period 3 don't obey the octet rule?

Sarah Fatkin 4I
Posts: 71
Joined: Fri Sep 28, 2018 12:27 am

Re: Exceptions to Octet Rule

Postby Sarah Fatkin 4I » Sun Nov 11, 2018 5:28 pm

Hi! All elements above period 3 can have an expanded octet.

Andrea Zheng 1H
Posts: 61
Joined: Fri Sep 28, 2018 12:26 am

Re: Exceptions to Octet Rule

Postby Andrea Zheng 1H » Sun Nov 11, 2018 5:28 pm

Elements in period 3 have an empty d-orbital, so it does not have to obey the octet rule. Hydrogen, helium, beryllium, and lithium are exceptions to the octet rule because they form duplets. Radicals are also exceptions to said rule.

anthony_trieu2L
Posts: 60
Joined: Fri Sep 28, 2018 12:29 am

Re: Exceptions to Octet Rule

Postby anthony_trieu2L » Sun Nov 11, 2018 5:39 pm

Although elements in period 3 and beyond have an expanded octet (due to their ability to access their d orbital), it does not necessarily mean that they don't obey the octet rule. It is always best to assign each element an octet when drawing Lewis structures and to determine the best and most stable structure from there (based on the formal charges).

Kevin Tang 4L
Posts: 83
Joined: Fri Sep 28, 2018 12:28 am

Re: Exceptions to Octet Rule

Postby Kevin Tang 4L » Sun Nov 11, 2018 5:51 pm

Andrea Zheng 3B wrote:Elements in period 3 have an empty d-orbital, so it does not have to obey the octet rule. Hydrogen, helium, beryllium, and lithium are exceptions to the octet rule because they form duplets. Radicals are also exceptions to said rule.


If radicals are exception to this rule, can they have nine valence electrons on their outer shell when they are not allowed to have an expanded octet (Nitrogen, Oxygen, Florine). Or do you mean by exception, that they can have seven valence electrons. If they have seven valence electrons, they have not exceeded the eight electrons on its outer shell.

Keshav Bhatnagar 1H
Posts: 32
Joined: Fri Sep 28, 2018 12:17 am

Re: Exceptions to Octet Rule

Postby Keshav Bhatnagar 1H » Sun Nov 11, 2018 8:28 pm

You should know that elements in the first and second periods can have expanded valence shells due to the empty d-orbital. You should also know that Cu and Cr have electron configuration exceptions.


Return to “Lewis Structures”

Who is online

Users browsing this forum: No registered users and 5 guests