hypervalent atoms

Atoms in and below the third row of the periodic table can sometimes have Lewis structures with more than 8 $e^{-}$ around them. Examples include $[S{O}_4{]}^{2-}$, $M{e}_{2}SO$, $P{h}_{3}PO$, or $S{F}_6$. Although it is traditional to draw these as having overfilled octets, it is always possible to depict resonance structures of them that do follow the octet rule (albeit with more formal charges).

TODO: figure with expanded octet vs charged versions of molecules.

Warning

You will likely encounter explanations for hypervalent atoms that claim hybridization using d-orbitals as an explanation. This is satisfying as an explanation, but accepted to be completely wrong. The difference in energy between s, p, and d orbitals is too large to hybridize, so hybridizations like $s{p}^3{d}^2$ are not based in reality. The bonding in these molecules is well-described by molecular orbital theory or quantum mechanical modeling, but Lewis structures aren’t quite up to the task. This is a reason organic chemists need to bel flexible with which models of bonding.