Salt

Summary: An ionic compound formed when the H⁺ in an acid is replaced by a metal ion or ammonium ion. Tags: igcse chemistry definition acids-bases Created: 2026-07-14 Last Updated: 2026-07-14

In chemistry, a salt is an ionic compound formed when the hydrogen ion (H⁺) of an acid is replaced by a metal ion or the ammonium ion (NH₄⁺), producing a crystalline solid composed of a positive cation and a negative anion held together by strong electrostatic forces in a giant ionic lattice. The name of a salt always has two parts — the first part comes from the metal or base used (e.g., sodium, copper(II), ammonium) and the second part comes from the parent acid following a predictable pattern: hydrochloric acid yields chlorides, sulfuric acid yields sulfates, nitric acid yields nitrates, ethanoic acid yields ethanoates, and carbonic acid yields carbonates. Salts can be prepared by several methods depending on the solubility of the target salt: reacting an acid with a metal produces salt and hydrogen gas; reacting an acid with an insoluble base or carbonate produces salt, water, and carbon dioxide where applicable; titration of an acid with an alkali yields a soluble salt of a Group 1 metal or ammonium; and precipitation from two aqueous solutions is used exclusively for preparing insoluble salts. In everyday life, salts are ubiquitous — sodium chloride is common table salt and road de-icer, calcium carbonate is limestone and chalk, ammonium nitrate is a vital nitrogenous fertiliser, and silver bromide is used in photographic film. For IGCSE, you must be able to name a salt given the acid and base, select the appropriate preparation method based on the solubility of the target salt, and write balanced chemical equations for each type of salt-forming reaction.

This is a key term definition page — part of the IGCSE Chemistry (0620/0971) keyword glossary.