An ion is a particle consisting of one or more atoms that carries a net electrical charge, formed when an atom or group of atoms gains or loses electrons. Ions are central to ionic compounds, electrolytes, and the conduction of electricity in solution. A positively charged ion such as Na⁺ is a cation, while a negatively charged ion such as Cl⁻ is an anion.

离子是由一个或多个原子组成、带净电荷的粒子,在原子或原子团得到或失去电子时形成。离子是离子化合物、电解质以及溶液导电的核心。带正电荷的离子(如 Na⁺)是阳离子,带负电荷的离子(如 Cl⁻)是阴离子。