The central atom in XeO64− is Xenon (Xe).
The number of valence electrons in Xe is 8.
Let the oxidation state of Xe in XeO64− be x.
x+6(−2)=−4
x=+8
Since the oxidation state of Xe is +8, all 8 of its valence electrons are involved in bonding with the 6 oxygen atoms. There are no non-bonding electrons left on the central atom.
Number of lone pairs on Xe =0
Xe forms 6 σ bonds with the 6 oxygen atoms (and 2 π bonds to satisfy its +8 oxidation state and minimize formal charge).
Number of σ bond-pairs =6
Total number of σ bond-pairs and lone pairs around the central atom =6+0=6.
Answer: 6