= Polyhedral skeletal electron pair theory
{title2=$n+1,\ n+2,\ n+3$}
= Wade's rules
{c}
{synonym}
An electron-counting approach relating <skeletal electron pairs> to a cluster vertex count $n$. A <closo> deltahedron has $n+1$ pairs; <nido> and <arachno> frameworks have $n+2$ and $n+3$. The count excludes electrons in externally directed bonds or <lone pairs>. It is a structural guide with a defined domain, not a rule that every molecule with the same total valence count has the same shape.
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