The hydroxide ion (OH−) is considered a nucleophile. This is because nucleophiles are species that donate an electron pair to form a chemical bond, and hydroxide possesses a lone pair of electrons on the oxygen atom. This electron-rich nature allows OH− to attract positively charged species (electrophiles) during reactions.
In contrast, electrophiles are electron-deficient and can accept an electron pair. They typically carry a positive charge or have a partial positive charge due to the presence of electronegative atoms in a molecule. Since OH− has the ability to donate electrons, it acts as a nucleophile in many organic and inorganic reactions, such as nucleophilic substitutions and additions.