The H2O molecule has four electron groups (two lone pairs and two bonding pairs).

• If we look only at the electrons, the electron geometry—the geometrical arrangement of the electron groups—is tetrahedral.
• The molecular geometry—the geometrical arrangement of the atoms—is bent.
• The lone pairs exert their influence on the bonding pairs.
• The bond angles in H2O actually are a few degrees smaller than the ideal tetrahedral angles (for reasons covered elsewhere).

Predicting the Shapes of Molecules with Lone Pairs on the Central Atom