"The sum of the number of atoms bonded to a central atom and the number of lone pairs formed by its nonbonding valence electrons is known as the central atom's steric number."

Wikipedia's entry about "Steric number"

I just started learning hybridisation and stuff for fun, and I just found out this "oddity".

  • 1
    $\begingroup$ This earlier answer relating to $\ce{IF5}$ may be helpful. $\endgroup$
    – ron
    Commented Aug 28, 2021 at 16:31

1 Answer 1


The steric number of $\ce{ClF_5}$ is 6, and this is possible because $\ce{sp^3}$ hybridization is not the maximum, or the 'limit' to hybridization. In the case of $\ce{ClF_5}$ the hybridization is $\ce{sp^3d^2}$, the hybridization involving the $\ce{3s}$, $\ce{3p}$ and $\ce{3d}$ orbitals.


Image credits: https://techiescientist.com/clf5-lewis-structure/


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