In which species is the central atom not surrounded by exactly 8 valence electrons?

In ${\mathrm{SF}}_4$  hybridization Given that S has 6 valence electrons and is covalently bonded to 4 F atoms, this means that 4 of S's valence electrons contribute to the establishment of the covalent link while the remaining 2 act as a lone pair. So, the total number of electrons that surround the central atom is 6 (the valence electron of the central atom) plus 4 (the electron that F acquires) = 10 electrons.