What is the structure of water?

• A. H2O2
• B. H2O
• C. HO2
• D. O2H

Answer: (B)

Water is a covalently bonded molecule made up of two hydrogen atoms attached to one oxygen atom, giving the formula H2O. The oxygen atom has two lone pairs of electrons, which repel the bonding pairs and bend the molecule to about 104.5 degrees. This shape makes water a polar molecule because oxygen is more electronegative than hydrogen, so the electrons are drawn toward the oxygen, producing a partial negative charge on oxygen and partial positive charges on the hydrogens. This polarity allows hydrogen bonding between water molecules, which is key to properties like its high boiling point and its role as a universal solvent. The other formulas correspond to different substances (for example, H2O2 is hydrogen peroxide), so they do not describe water.