What is the formula for the hydroxide ion?

The hydroxide ion is represented by the formula OH(-). This ion consists of one oxygen atom covalently bonded to one hydrogen atom, and it carries a negative charge. The presence of the negative charge indicates that the hydroxide ion has gained an extra electron, resulting in its overall charge of -1.

Understanding the composition of hydroxide is key: oxygen typically forms two bonds and has six valence electrons, while hydrogen has one valence electron. When they combine to form hydroxide, oxygen shares one of its electrons with hydrogen, but it also possesses an extra electron, thus creating the anionic species. This ion plays an important role in various chemical reactions, particularly in acid-base chemistry where it can react with protons (H+) to form water.

In contrast, the other choices do not represent the hydroxide ion. Water is a molecule made of two hydrogen atoms and one oxygen atom, while O2(2-) indicates a superoxide ion, and CO3(2-) represents the carbonate ion, both of which consist of different arrangements and compositions of atoms. Therefore, the representation of hydroxide as OH(-) is both accurate and significant in understanding its function in chemistry.