Sodium is a chemical element with atomic number 11 and the element symbol Na, which belongs to the group of alkali metals. Sodium is a monovalent
cation , which is important in
water treatment , especially in
water softening and water de-iron removal through
ion exchange . Due to its monovalent nature, the
exchange resin in a softening system strives to release the sodium into the water and exchange it for divalent
calcium and
magnesium . This is how
water softening works because the two substances
calcium and
magnesium are removed from the water. This removes the
limescale from the water, so to speak.