The d orbital comes into play when the central atom has more than 8 valence electrons. That's called an expanded octet and can happen when the central atom is in the third row of the periodic table or lower (as sulfur is).
When you draw the Lewis structure for SF4 you see that it has four single sulfur-fluorine bonds, but then you have an additional pair of electrons that must go on the central sulfur atoms as a lone pair. That's five electron groups surrounding the sulfur atom, and sp3 hybridization can only accommodate four electron groups. The fifth hybridized orbital comes from the sulfur atom's potential (but unoccupied in the unbonded atom) 3d sublevel.
I hope that helps. Good luck!
You should first understand that there are types of hybridization like sp,sp2,sp3,sp3d,dsp2,sp3d2,d2sp3. I will give you some examples:
Go to this site to see picture of SF4
I had to leave a line between the // and en…. or yahoo answers will not copy the address
You rewrite this address continuously from http:// to .htm, copy, paste it as address and you will see SF4 molecule
thank you alot for answering that qn i was also wondering where the d comes frm. thnk you too for posting the question.