Lewis structure of SF₄
34 valence electrons. Four S-F single bonds, with one lone pair on S, so S has 10 electrons around it (an expanded octet).
Lewis structure
34 valence electronsFormal charges: none
Why this shape
- S has 6 valence electrons. It uses four in four single bonds to F, so two are left as one lone pair.
- Steric number = four sigma bonds + one lone pair = 5, so S is sp³d hybridised.
- Five electron pairs point to the corners of a trigonal bipyramid (trigonal bipyramidal electron geometry). With one lone pair in place of atoms, the atoms make a see-saw shape.
- The lone pair takes an equatorial position, where it is 90 degrees from only two bond pairs.
- The lone pair takes an equatorial position and pushes the bonds away: the equatorial angle closes from 120 to about 102 degrees and the axial bonds bend back from 180 to about 173.
- The bond dipoles do not cancel in the see-saw shape, so SF₄ is polar.
How to draw it
- Count the valence electrons: S 6 + 4 × F 7 = 34 valence electrons, 17 pairs.
- Put S in the middle and join it to the four outer atoms with single bonds.
- Give each outer atom lone pairs until it has an octet (H needs only two electrons), then put any electrons left over on the central atom.
- Result: four S-F single bonds, with one lone pair on S, so S has 10 electrons around it (an expanded octet).
- Formal charge = valence electrons − lone pair electrons − number of bonds. Here: none.
Class 11, Chapter 4 Chemical Bonding and Molecular Structure.
Lewis structure of SF4: quick answers
How many valence electrons are in SF4?
S 6 + 4 × F 7 = 34 valence electrons, 17 pairs.
What are the formal charges in the Lewis structure of SF4?
Every atom has a formal charge of zero.
How many lone pairs are in the Lewis structure of SF4?
13 in all, 1 of them on the central S.