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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: SF3N.gif
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
SF3N
The geometry of trifluorothionitrile, F3S≡N. You can use your mouse to rotate the molecule in the right hand "JMol" image.

A VSEPR tutorial on the WWW

VSEPR tutorial on the WWW, URL: http://winter.group.shef.ac.uk/vsepr/
Copyright 1996-2015 Prof Mark Winter [The University of Sheffield]. All rights reserved.
Document served: Wednesday 26th April, 2017