What is the formula for hydroxide?

Hydroxide is represented by the formula OH-. This ion consists of one oxygen atom and one hydrogen atom, and it carries a negative charge. It is important in various chemical reactions, particularly in acid-base chemistry, where it acts as a base. The presence of the negative charge is significant because it indicates that hydroxide can accept a proton (H+) to form water (H2O).

The other choices represent different ions: CrO4^2- is the chromate ion, CO3^2- is the carbonate ion, and NO2- is the nitrite ion. These ions have different compositions and charges, which makes them distinct from hydroxide, reinforcing that OH- is the correct representation for the hydroxide ion.