Electrically charged atom or molecule
Cations are positive, anions negative
An ion is an atom or molecule that carries an electric charge because it has gained or lost electrons. Positively charged ions are called cations, such as sodium (Na⁺) and potassium (K⁺), while negatively charged ions are called anions, such as chloride (Cl⁻). Oppositely charged ions attract each other and can form ionic bonds. In cells, dissolved ions create membrane potentials, transmit nerve signals, and help many enzymes work.