There are no nonbinding pairs on the central Si atom in ${\mathrm{SiF}}_4$ after the 31 valence electrons have been dispersed among the atoms to form bonds and put lone pairs. The Si atom in the center, which is surrounded by 8 electrons and so 4 bonding pairs, follows the octet rule. The fact that each F atom is surrounded by 8 valence electrons—3 nonbinding pairs and 1 bonding pair—means that all the F atoms likewise follow the octet rule.