Common salt (sodium chloride being its scientific name) is the best known example of the large, important group of compounds known collectively as "salts". Sodium chloride displays many of the properties associated with salts and, in many ways, is a typical salt. We will first investigate the properties of common salt and then expand on this knowledge to find out more about salts in general in the topic Ions and salts.

Common salt - sodium chloride
Salt is a clear, white, crystalline solid with a high melting point of 801°C. It shatters when hit with a hammer, forming many smaller crystals. Salt will not cut like wood or butter, but will cleave along a straight face. It is quite soluble in water, but will not dissolve in petrol or other liquid hydrocarbons.

Salt is collected by two common methods: mining "rock salt" from underground salt deposits, laid down millions of years ago by old oceans and seas, or by evaporating off the water from sea water leaving behind "sea salt". Chemically, rock salt and sea salt are the same - sodium chloride with traces of other minerals and salts. They differ only in the size of their crystals, with rock salt usually having larger crystals.

Made of ions
Sodium chloride is made from sodium ions and chloride ions. The formula for sodium chloride is NaCl. Both sodium and chloride ions are very common on Earth, being found in the oceans, rocks and soil.

In salt water solution, sodium and chloride ions move about independent of each other. In solid form however, these two ions form a close one-to-one relationship.

Salt crystals are not the same as molecules where two or more atoms combine to form single discrete molecules. In an ionic salt crystal a lattice of sodium and chloride ions is formed which grows into a crystal. The formula NaCl tells us that the ratio of sodium ions (Na+) to chloride ions (Cl-) is one-to-one but, unlike in a molecule, the actual number of ions in a single crystal can be incredibly large.