H2O is the chemical formula for water. Each water molecule has two hydrogen atoms and one oxygen atom. Each hydrogen atom is attached to the oxygen atom with a polar covalent bond.
The hydrogens form a 104.5-degree angle with one another. The oxygen has two extra electron pairs that distort the structure from the regular tetrahedral angle of 109.5. The scientific name for water is dihydrogen oxide. A water molecule is neutrally charged, but the oxygen atom is more negative because it attracts the electrons more strongly than the hydrogen atoms. Because of its unique structure, water is one of the only compounds that is less dense as a solid than as a liquid.