To determine theorbital hybridizationof the sulfur atom, which is the central atom in sulfur tetrafluoride, start by darawing the molecule'sLewis structure.

The molecule will have a total of34valence electrons,6from sulfur, and7from each of the four fluorine atoms.

The sulfur atom will formsingle bondswith each of fluorine atoms. These bonds will account for8of the34valence electrons. Each fluorine atom will have3 lone pairs of electronsin order to have a completeoctet.

These lone pairs will use up24valence electrons, bringing the total of used valence electrons to32. The remaining two electrons will be placed on the sulfur atom as alone pair

Now focus on the sulfur atom. Notice that it gets a total of 10 electrons, 8 from the bonds with fluorine and 2 from the lone pair. This is quite possible for sulfur because it has easy access to its 3d-orbitals, which means that it canexpand its octetand accomodate more than 8 electrons.

You determine sulfur's hybridization by counting the number of regions ofelectron densitythat surround it. Remember, a region of electron density is a bond (single, double, and triple bonds count asoneregion of electron density) or a lone pair of electrons.

In this case, sulfur forms4single bonds and has1lone pair, which means that itssteric number, which is the name given to the number of regions of electron density, is equal to5.

The steric number will give you the number of hybrid orbitals that the atom uses. In this case, sulfur will usefive hybrid orbitalsformed from