An ion is an atom or group of atoms that has an electric charge. Ions with a positive charge are called cations. Ions with a negative charge are called anions.
Many normal substances exist in the body as ions. Common examples include sodium, potassium, calcium, chloride, and bicarbonate. (See: Electrolytes)
Ions can be created using radiation such as x-rays. Ionizing radiation is often used for diagnostic or therapeutic procedures, since the ions that are produced can be used to scan for or treat some diseases.
David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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