Sodium

Sodium (chemical symbol Na) is an electrolyte used in many bodily processes, including muscle and nerve function. Along with potassium and magnesium, it has an important role in ion transportation. Sodium is often consumed in the form of common/table salt (sodium chloride), and plays an important role in regulating blood volume and therefore blood pressure. The body excretes sodium in sweat and urine. Normal blood sodium is between 135 and 145 milliequivalents per liter (mEq/L); levels below this cause cells to swell with excess water, a condition known as hyponatremia.

Molecular forms of sodium
Pure sodium is highly reactive, tarnishing within seconds of exposure to air and reacting violently with water. Because of this, all naturally-occurring sodium is bonded to at least one other atom in a molecule. Common salt, or sodium chloride, is the most abundant sodium-containing molecule on Earth. Other common sodium-containing molecules include baking soda and washing soda.

Sodium chloride (common or table salt)
Sodium chloride (molecular formula NaCl) is one of the most abundant minerals on earth, occurring naturally in sea salt and underground rock formations. Each molecule consists of one atom of sodium and one atom of chlorine. A solution of sodium chloride dissolved in water is known as saline, commonly used in intravenous fluids.

Learn more

 * Linus Pauling Institute Micronutrient Information Center - Sodium (Chloride)