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ScienceQuest

Sulfur hexafluoride (SF₆) Lewis structure

48 valence electrons, octahedral

S F F F F F F
SF₆ as the Lewis Structure Generator draws it: lone pairs as dots.

Build SF₆ step by step in the Lewis Structure Generator

What is the Lewis structure of SF₆?

Sulfur hexafluoride, SF₆, has 48 valence electrons. Sulfur is the central atom, joined by six S−F single bonds. It carries three lone pairs on each F. Every formal charge is zero. S is AX₆: octahedral, with ideal bond angles of 90° and 180°, and the molecule is nonpolar.

Valence electrons in SF₆

Element Group Valence electrons Atoms Electrons
Sulfur 16 6 1 6
Fluorine 17 7 6 42
Total 48

In one line: 6 + 6 × 7 = 48. Each atom brings the valence electrons its group gives it.

How to draw the SF₆ Lewis structure

  1. Count the valence electrons. Valence electrons: S 6 and each F 7. 6 + 6 × 7 = 48.
  2. Choose the central atom. S goes in the middle: S is the least electronegative atom other than H, χ 2.58 against 3.98 for F.
  3. Join the atoms with single bonds. Six single bonds use 12 electrons, leaving 48 − 12 = 36.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 6 F × 6 = 36, leaving 36 − 36 = 0.
  5. Put the rest on the central atom. Nothing is left, so S gets no lone pair, and S now has 12 electrons round it. That is more than eight, which an atom from period 3 on can hold.
  6. Make multiple bonds where needed. Every atom already has an octet or more, so no lone pair needs to become a bond.

Lone pairs and formal charges in SF₆

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
S (central) 1 six single bonds 0 12 6 − 0 − 6 = 0
F 6 one single bond 3 8 7 − 6 − 1 = 0

V is the atom’s valence electrons, N its nonbonding electrons and B its bonding electrons. The formal charges add up to 0, the molecule’s overall charge.

Shape and polarity of SF₆

Central atom S
VSEPR class AX₆
Electron geometry octahedral
Molecular geometry octahedral
Ideal bond angles 90° and 180°
Measured bond angle 90°
Polarity, an estimate nonpolar

In an octahedral shape identical bonds cancel exactly.

S has six σ bonds and no lone pairs, six electron domains in all, so its electron geometry is octahedral. With no lone pairs, the molecular geometry is the same.

The VSEPR Molecular Geometry viewer turns the AX₆ shape in 3D, lone pairs included.

The measured angle is the accepted experimental value the VSEPR viewer quotes for this molecule.

Work with SF₆