VSEPR calculation for trifluorothionitrile, SF₃N

Note that the net effect of a triple bonded group such as ≡N is -1, made up from +1 in the σ bond and -2 for the two π bonds. As for a double bond, the S≡N bond takes up more room than a single bond and this causes the F₃S≡N F-S-F bond to drop a little below the ideal tetrahedral bond angle.

Trifluorothionitrile, F₃S≡N

Lewis structure:
Central atom:	sulphur
Valence electrons on central atom:	6
3 F atoms each contribute 1 electron:	3
1 terminal nitrogen contributes 1 electron in a σ bond	1
Subtract two for the two electrons contributed by S to the two π bonds	-2
Total:	8
Divide by 2 to give electron pairs	4
4 electron pairs:	tetrahedral geometry for the four shape-determining electron pairs

The geometry of trifluorothionitrile, F3S≡N. You can use your mouse to rotate the molecule in the right hand "JMol" image.