Salt: definition in chemistry
Salt: An ionic compound made of positive ions (cations) and negative ions (anions), typically formed when an acid reacts with a base. Table salt, sodium chloride, is the best-known example.
In a neutralization, the cation of the salt usually comes from the base and the anion from the acid, as when hydrochloric acid and sodium hydroxide form sodium chloride and water. Salts are named with the cation first and the anion second, as in potassium nitrate. Not all salts are neutral: dissolving sodium acetate gives a slightly basic solution, while ammonium chloride gives a slightly acidic one.
Examples
- Sodium chloride (NaCl) — table salt
- Calcium carbonate (CaCO₃) — limestone, chalk and seashells
- Copper(II) sulfate (CuSO₄) — forms blue crystals when hydrated
- Ammonium nitrate (NH₄NO₃) — a common fertilizer
On the periodic table
The halogens of group 17 get their name from the Greek for salt-former, because they combine directly with metals to make salts such as NaCl and KBr.