What does it mean for an atom/molecule to be electron rich? For instance, why is the methyl carbanion considered electron rich (having excess electrons) even though it has a complete octet, no more, no less? I know that if the octet is incomplete, an atom/molecule is considered electron deficient, but how exactly is electron richness defined? I was under the impression that electron richness referred to atoms/molecules which had more than 8 electrons on the central atom.

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    $\begingroup$ These are just wording used by organic chemists. It has nothing to do with reality. What is experimentally realizable is the electron density by X-ray measurements. The rest is all hand-waving spam. $\endgroup$
    – AChem
    Aug 22, 2021 at 18:04
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    $\begingroup$ It is electron rich as it still has electrons to spare for bond formation. $\endgroup$ Aug 23, 2021 at 6:23
  • $\begingroup$ Like temperature, without established reference, there is no comparison possible. A reasonable comparison would be like «There are more $\pi$ electrons per non-H atom in pyrrole than in benzene; thus the $\pi$ electron density in pyrrole is higher than the one in benzene and considered electron rich.» If not reformulated, the question will attract opinions instead of answers backed by evidence. $\endgroup$
    – Buttonwood
    Aug 25, 2021 at 20:14


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