An unpaired electron refers to an electron in an atom or molecule that is alone in its orbital and does not have a corresponding electron with opposite spin. Electrons occupy atomic orbitals in pairs, with one electron spinning in one direction (spin-up) and the other in the opposite direction (spin-down). When an orbital contains a single electron, that electron is considered an unpaired electron. Unpaired electrons are significant in determining the chemical properties and reactivity of atoms and molecules.
