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Xenon trioxide (XeO₃) Lewis structure

26 valence electrons, trigonal pyramidal

Xe O O O
XeO₃ as the Lewis Structure Generator draws it: lone pairs as dots.

Build XeO₃ step by step in the Lewis Structure Generator

What is the Lewis structure of XeO₃?

Xenon trioxide, XeO₃, has 26 valence electrons. Xenon is the central atom, joined by three Xe=O double bonds. It carries one lone pair on the central Xe and two on each O. Every formal charge is zero. Xe is AX₃E₁: trigonal pyramidal, with an ideal bond angle of 109.5°, and the molecule is polar.

Valence electrons in XeO₃

Element Group Valence electrons Atoms Electrons
Xenon 18 8 1 8
Oxygen 16 6 3 18
Total 26

In one line: 8 + 3 × 6 = 26. Each atom brings the valence electrons its group gives it.

How to draw the XeO₃ Lewis structure

  1. Count the valence electrons. Valence electrons: Xe 8 and each O 6. 8 + 3 × 6 = 26.
  2. Choose the central atom. Xe goes in the middle: Xe is the least electronegative atom other than H, χ 2.60 against 3.44 for O. Checked the other way, O in the middle would need an O−O bond, and electronegative atoms of one element avoid bonding to each other when they can.
  3. Join the atoms with single bonds. Three single bonds use 6 electrons, leaving 26 − 6 = 20.
  4. Complete the outer atoms. Each outer atom takes enough lone pairs to reach eight: 3 O × 6 = 18, leaving 20 − 18 = 2.
  5. Put the rest on the central atom. The 2 left go on the central atom as one lone pair on Xe, and Xe now has 8 electrons round it.
  6. Make multiple bonds where needed. Xe already has an octet, but turning three lone pairs into three Xe=O bonds lowers its formal charge from +3 to 0. That is what the smallest formal charges convention asks for; octets first stops a step earlier.

Lone pairs and formal charges in XeO₃

Atom Number Bonds Lone pairs Electrons round it Formal charge, V − N − B/2
Xe (central) 1 three double bonds 1 14 8 − 2 − 6 = 0
O 3 one double bond 2 8 6 − 4 − 2 = 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.

XeO₃ with an octet on every atom

The structure above keeps the formal charges as small as they go and puts 14 electrons round Xe. Keeping every atom to eight instead, the octets-first convention, gives one form: three Xe−O single bonds, with formal charges of +3 on the central Xe and −1 on each O. Courses differ on which of the two they expect.

Xe O O O 3+ − − −
Octets first

Octets first puts +3 on xenon. The smallest formal charges convention avoids it with expanded octets.

Draw XeO₃ with octets first in the Lewis Structure Generator

Shape and polarity of XeO₃

Central atom Xe
VSEPR class AX₃E₁
Electron geometry tetrahedral
Molecular geometry trigonal pyramidal
Ideal bond angle 109.5°
Polarity, an estimate polar

The trigonal pyramidal shape leaves the bond dipoles unbalanced.

Xe has three σ bonds and one lone pair, four electron domains in all, so its electron geometry is tetrahedral. Counting only the bonded atoms, the molecular geometry is trigonal pyramidal.

The VSEPR Molecular Geometry viewer turns the AX₃E₁ shape in 3D, lone pairs included.

Work with XeO₃