Charge: -1

The hydroxide ion is a polyatomic ion, meaning it is composed of multiple atoms. In this case, it is composed of one oxygen atom and one hydrogen atom. The oxygen atom has a charge of -2, while the hydrogen atom has a charge of +1. This gives the hydroxide ion an overall charge of -1.

Hydroxide ions are found in many different compounds, including water (H2O), sodium hydroxide (NaOH), and potassium hydroxide (KOH). They are also found in many biological systems, where they play an important role in maintaining the pH balance of cells and tissues.