H2O Lewis Structure
The Lewis dot structure of water (H2O): oxygen in the centre with a single bond to each hydrogen and two lone pairs, giving a bent shape.
How to draw the Lewis structure of H2O
- Count valence electrons: O has 6, each H has 1, so the total is 6 + 1 + 1 = 8 electrons.
- Put oxygen in the centre (hydrogen can only ever form one bond) and join each hydrogen with a single bond (4 electrons used).
- Place the remaining 4 electrons as two lone pairs on oxygen. Oxygen now has 2 bonds + 2 lone pairs = 8 electrons, and each hydrogen has 2.
Worked example: counting electron domains
Oxygen has 4 electron domains (2 bonding pairs, 2 lone pairs), so the electron geometry is tetrahedral. Molecular shape only counts the atoms, not the lone pairs, so removing the two lone pairs from the picture leaves a bent shape with a bond angle compressed from 109.5° to about 104.5°.
Compare it with the NH3 Lewis structure (3 bonds, 1 lone pair, pyramidal) and check any shape on the VSEPR chart, then build H2O in 3D in the Molecule Builder.
Frequently asked questions
How many valence electrons does H2O have?
Eight. Oxygen has 6 and each hydrogen has 1, so 6 + 1 + 1 = 8 valence electrons.
Why does water have a bent shape?
Oxygen has four electron domains: two bonds to hydrogen and two lone pairs. All four push apart into a tetrahedral arrangement, but only the two bonded atoms are counted for shape, so the molecule looks bent.
Why is the bond angle 104.5° and not 109.5°?
A perfect tetrahedron has 109.5° angles, but the two lone pairs on oxygen take up more space than bonding pairs and push the two O-H bonds slightly closer together, down to 104.5°.
Is water polar or nonpolar?
Polar. Oxygen is far more electronegative than hydrogen, and the bent shape means the two O-H bond dipoles do not cancel, leaving the oxygen end slightly negative and the hydrogens slightly positive.
