Sodium Chloride: The Molecular Formula of Table Salt

Learn why it doesn't truly cover the true chemical composition of salt

Sodium chloride
Pure table salt is sodium chloride, with the formula NaCl. Equal numbers of sodium and chlorine atoms are arranged in a crystal ionic lattice. LAGUNA DESIGN / Getty Images

Table salt is an ionic compound, which breaks into its component ions or dissociates in water. These ions are Na+ and Cl-. The sodium and chlorine atoms are present in equal amounts (1:1 ratio), arranged to form a cubic crystal lattice. The molecular formula of table salt—sodium chloride—is NaCl.

In the solid lattice, each ion is surrounded by six ions having an opposite electrical charge. The arrangement forms a regular octahedron. The chloride ions are much larger than the sodium ions. The chloride ions are arranged in a cubic array with respect to one another, while the small sodium cations fill the gaps between the chloride anions.

Why Table Salt Isn't Really NaCl

If you had a pure sample of sodium chloride, it would consist of NaCl. However, table salt actually isn't pure sodium chloride. Anti-caking agents may be added to it, plus most table salt is supplemented with the trace nutrient iodine. While ordinary table salt (rock salt) is purified to contain mostly sodium chloride, sea salt contains many more chemicals, including other types of salt. The natural (impure) mineral is called halite.

One way to purify table salt is to crystallize it. The crystals will be relatively pure NaCl, while most impurities will remain the solution. The same process may be used to purify sea salt, although the resulting crystals will contain other ionic compounds.

Sodium Chloride Properties and Uses

Sodium chloride is vital for living organisms and important for industry. Most of the salinity of seawater is due to sodium chloride. The sodium and chloride ions are found in the blood, hemolymph, and extracellular fluids of multicellular organisms. Table salt is used to preserve food and enhance flavor. It's also used to de-ice roads and walkways and as a chemical feedstock. Salt may be used as a cleaning agent. Fire extinguishers Met-L-X and Super D contain sodium chloride to extinguish metal fires.

IUPAC Name: sodium chloride

Other Names: table salt, halite, sodium chloric

Chemical Formula: NaCl

Molar Mass: 58.44 grams per mole

Appearance: Pure sodium chloride forms odorless, colorless crystals. Many small crystals together reflect light back, making the salt appear white. The crystals may assume other colors if impurities are present.

Other Properties: Salt crystals are soft. They are also hygroscopic, which means they readily absorb water. Pure crystals in the air eventually develop a frosted appearance due to this reaction. For this reason, pure crystals are often sealed in a vacuum or completely dry environment.

Density: 2.165 g/cm3

Melting Point: 801 °C (1,474 °F; 1,074 K) Like other ionic solids, sodium chloride has a high melting point because significant energy is required to break ionic bonds.

Boiling Point: 1,413 °C (2,575 °F; 1,686 K)

Solubility in Water: 359 g/L

Crystal Structure: face-centered cubic (fcc)

Optical Properties: Perfect sodium chloride crystals transmit about 90% of light between 200 nanometers and 20 micrometers. For this reason, salt crystals may be used in optical components in the infrared range.