Health Library

Ions

Cations; Anions

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. These substances are known as electrolytes.

Ions can be created using radiation such as x-rays. Ionizing radiation is often used to diagnose or treat a medical condition.

Related Information

References

Farley P, Smith SG, Sperry JL, Schreiber MA. Shock, electrolytes, and fluid. In: Tyler DS, Hayes-Dixon A, Hines OJ, et al, eds. Sabiston Textbook of Surgery: The Biological Basis of Modern Surgical Practice. 22nd ed. Philadelphia, PA: Elsevier; 2026:chap 33.

Kapoor G, Toms AP. Current status of imaging of the musculoskeletal system. In: Adam A, Dixon AK, Gillard JH, Schaefer-Prokop CM, eds. Grainger & Allison's Diagnostic Radiology. 7th ed. Philadelphia, PA: Elsevier; 2021:chap 38.

Taber's Cyclopedic Medical Dictionary. Ions. 24th ed. Philadelphia, PA: F.A. Davis Company; 2021. www.tabers.com/tabersonline/view/Tabers-Dictionary/769859/all/ion. Accessed October 9, 2025.

Review Date: 10/1/2025  

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