Octahedral Arrangement

[Anisha Chandra 1K]

Why can't a central atom have more than 6 bonds/lone pairs? This allows for 12 electrons which is already an expanded octet, but why can't it expand more if the d subshell has 10 electrons and s, p, and d together have 18 electrons?

[Gerald Bernal1I]

The lewis structures are only showing the valence electrons which with the octet rule means 8 electrons in order for the atom to be stable. Expanding the octet with atoms that are able to just depends on the formal charge of the atoms and what would ultimately lead to a stable structure.

[AnnikaMittelhauser4E]

The textbook does mention a pentagonal bipyramidal structure which is 7 regions of electron density, but I don't see anything past that. Maybe molecules past 7 regions of electron density don't really exist due to too much electron repulsion or something - the bond angles get too small? Or, they're super complicated so they aren't mentioned. Interesting question.