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[Gr. iōn, iont-, going ]
An atom or group of atoms that has lost one or more electrons and has a positive charge, or has gained one or more electrons and has a negative charge. In aqueous solutions, ions are called electrolytes because they permit the solution to conduct electricity. Positive ions such as sodium, potassium, magnesium, and calcium are called cations; negative ions such as chloride, bicarbonate, and sulfate are called anions. In body fluids, ions are available for reactions, e.g., calcium ions from food may be combined with carbonate ions to form calcium carbonate, part of bone matrix.
SEE: electrolyte for table
Ions occur in gases, esp. at low pressures, under the influence of strong electrical discharges, x-rays, and radium; and in solutions of acids, bases, and salts.