What is the molecular structure of water vapor?

Air is a mixture of gases.. so it desn't have any appropriate molecular structure.. The composition of air is : Nitrogen (N2): 78.09% Oxygen (O2): 20.95% Argon (Ar): 0.93% Carbon dioxide (CO2): 0.038% Others (less than 0.002% each): Neon (Ne), Helium (He), Krypton (Kr), Hydrogen (H2), Xenon (Xe).