Chemically, water is a compound of hydrogen and oxygen, having the formula H 2 O. It is chemically active, reacting with certain metals and metal oxides to form bases, and with certain oxides of nonmetals to form acids. It reacts with certain organic compounds to form a variety of products, e.g., alcohols from alkenes. Because water is a polar compound, it is a good solvent. Although completely pure water is a poor conductor of electricity, it is a much better conductor than most other pure liquids because of its self-ionization, i.e., the ability of two water molecules to react to form a hydroxide ion , OH - , and a hydronium ion, H 3 O + . Its polarity and ionization are both due to the high dielectric constant of water.