The Lewis structure of water has oxygen in the center, two O–H single bonds and two lone pairs on oxygen. Those four electron domains produce a bent molecular shape.
Oxygen contributes six valence electrons and the two hydrogen atoms contribute one electron each, giving eight electrons in total. Two pairs are used to form O–H bonds. The remaining four electrons stay on oxygen as two lone pairs.
Hydrogen follows the duet rule, so each H is complete after forming one single bond. Oxygen has eight electrons around it when the two bonds and two lone pairs are counted.
How to draw the H2O Lewis structure
Count the electrons.
Oxygen provides 6 and two hydrogens provide 2, for a total of 8 valence electrons.
Choose the central atom.
Hydrogen cannot be central because it forms only one bond, so oxygen goes in the middle.
Draw two single bonds.
Connect oxygen to both hydrogens. The two bonds use 4 electrons.
Place the remaining electrons.
Put the final 4 electrons on oxygen as two lone pairs.
Check the electron count.
Each H has 2 electrons and O has an octet. All 8 valence electrons are represented.
Formal charges
The standard structure has a formal charge of zero on every atom. Oxygen owns four nonbonding electrons and half of the four bonding electrons, matching its six valence electrons.
Geometry and polarity
Four electron domains around oxygen give a tetrahedral electron-domain arrangement. Because two domains are lone pairs, the molecular geometry is bent. The O–H bond dipoles do not cancel, so water is polar.
Common mistakes
Drawing water as a linear molecule. Lone-pair repulsion bends the H–O–H arrangement.
Forgetting one or both lone pairs on oxygen.
Adding double bonds to hydrogen. Hydrogen can only have two electrons.
Using more or fewer than eight total valence electrons.
Frequently asked questions
How many lone pairs does H2O have?
There are two lone pairs, both located on the oxygen atom.
Why is H2O bent instead of linear?
The two lone pairs repel the bonding pairs more strongly and compress the H–O–H angle to about 104.5°.
What is oxygen's hybridization in H2O?
In the common valence-bond model, oxygen is described as sp³ hybridized because it has four electron domains.