## Easy way to remember octet exceptions

Katherine Brenner 3H
Posts: 73
Joined: Wed Sep 18, 2019 12:18 am

### Easy way to remember octet exceptions

Hello

Is there any easy way to remember the octet exceptions?

Sebastian Lee 1L
Posts: 157
Joined: Fri Aug 09, 2019 12:15 am
Been upvoted: 1 time

### Re: Easy way to remember octet exceptions

Basically, if the element is in the 3rd row of the periodic table or beyond, it can have an expanded octet. For incomplete octets, it's H, He, Li, Be, B and the rest of the group 13 elements (like Al).

chrischyu4a
Posts: 52
Joined: Thu Jul 25, 2019 12:16 am

### Re: Easy way to remember octet exceptions

Also it is helpful to check the formal charge on the central ion as expanded octets usually contribute to decreasing the formal charge to 0.

Jorge Ramirez_4H
Posts: 54
Joined: Wed Nov 21, 2018 12:19 am

### Re: Easy way to remember octet exceptions

There are only 3 exceptions right?

Posts: 107
Joined: Sat Aug 17, 2019 12:16 am
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### Re: Easy way to remember octet exceptions

Any atom with a d orbital has the octet exception. Atoms in row one and two only have the p and s orbitals and thus eight valence electrons, the p orbital has six and the s orbital two. With the addition of a d orbital, atoms are able to accommodate more than eight valence electrons by putting some in the d orbital which can accept ten electrons. Since the d orbital start in the n=3 row then any atom from n=3 and below can have an expanded octet.