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Octet exception

Posted: Thu Oct 31, 2019 4:44 pm
by Jina Kwon
What causes a molecule to have an octet exception?

Re: Octet exception

Posted: Thu Oct 31, 2019 4:57 pm
by Alex Chen 2L
Depends on what kind of exception. Elements in period 3 and above such as phosphorus, sulfur, and chlorine can hold more than 8 valence electrons due to having a d-orbital. This leads to molecules such as PCl5 where phosphorus holds 10 valence electrons. On the other hand, elements such as boron and aluminum can have less than 8 valence electrons due to their involvement in Lewis Acid-Base reactions. There are also compounds called radicals that have an atom that has only 7 valence electrons (one unpaired electron).

Re: Octet exception

Posted: Thu Oct 31, 2019 6:35 pm
by Lindsey Chheng 1E
Jina Kwon wrote:What causes a molecule to have an octet exception?

Some atoms are stable with fewer electrons, which doesn't meet the octet rule: H, He, Li, Be, B. In class, Dr. Lavelle talked about how B and Al are involved in Lewis Acid-Base reactions, where B in BF3 completes its octet if other atom provides both electrons to form a coordinate covalent bond.