Hydroxide ion
Charge: 1- · Type: Polyatomic anion · Molar mass: 17.007 g/mol
Made of: oxygen, hydrogen
How it forms
Water splits very slightly into H+ and OH-, and bases like sodium hydroxide release OH- directly when they dissolve. The ion's negative charge sits mainly on the oxygen atom.
Naming note
OH- is the hydroxide ion. Bases are named as hydroxides of metals (sodium hydroxide), while the -OH group in organic molecules is called a hydroxyl group instead.
Examples in compounds
Sodium hydroxide
Calcium hydroxide
Potassium hydroxide