Which mineral commonly appears with sodium and chloride as electrolytes?

• A. Calcium
• B. Potassium
• C. Magnesium
• D. Phosphorus

Answer: (B)

Electrolytes are charged minerals that dissolve in body fluids and enable electrical activity essential for nerves, muscles, and fluid balance. Sodium and chloride are the primary extracellular electrolytes, forming the fluid environment outside cells. Potassium is the main intracellular cation and is routinely discussed alongside sodium and chloride because together they govern membrane potentials and the transmission of nerve impulses and muscle contractions. This pairing highlights how ions inside and outside cells coordinate to keep fluids balanced and cells function properly. Calcium, magnesium, and phosphorus are important electrolytes too, but they’re tied to other roles—calcium with bone and signaling, magnesium as a enzyme cofactor and NMJ support, and phosphorus as phosphate involved in energy and acid-base balance—so they aren’t the trio usually emphasized with sodium and chloride.