Antimony forms chemical compounds in three oxidation states: -3, +3, and +5. -3 compounds are called antimonides. They are made by reacting antimony with other metals. They react with acids to make the toxic and unstable gas stibine. +3 compounds are the most common. They are weak oxidizing agents. They are somewhat covalent, having low melting points. Antimony trichloride is a colorless and soft solid that has a strong odor. Antimony trioxide is a white solid that dissolves a little in water. The other antimony(III) halides all react with water except for antimony trifluoride. +5 compounds are strong oxidizing agents. Antimony pentafluoride is highly reactive, as well as antimony pentoxide.