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Expanded Octets

Posted: Thu Nov 22, 2018 4:00 pm
by paytonm1H
In the textbook, it states that in PCl5, the P atom expands its valence shell to ten electrons by using one d-orbital. Wouldn't the lowest energy be if the P atom used two d-orbitals with the two electrons having the same spin (Hund's Rule)? Why do they only fill one orbital?
Thanks!

Re: Expanded Octets

Posted: Thu Nov 22, 2018 7:08 pm
by Tarika Gujral 1K
A bond is only formed if it is energetically favorable, meaning that electrons in a bond have a lower energy then free electrons. Thus, it is more energetically favorable to fill 1 d orbital and have all electrons in a bond, as opposed to having electrons in a free orbital.