Inorganic compounds contain atoms linked together via ionic bonds and, on dissolving in water, split up into cations and anions. Cations are positively charged ions. When a neutral atom loses one or more electrons, it forms cations with one or more positive charges. Salts are formed by the complete or partial neutralization of an acid with a base or vice-versa. The part of a salt contributed by the acid is known as an anion, while the part contributed by the base is known as a cation. For example, in the case of ZnSO₄ and NaCl, Zn²⁺ and Na⁺ ions are cations and (SO₄)^2- and Cl^– ions are anions.

Characteristic tests are carried out to detect the presence of cations in the compound. Tests are of two types, positive and negative. While doing a test, one is concerned with the formation or the disappearance of (i) colour, (ii) a precipitate, and (iii) a gas. If a test is done and gives the same result as the procedure, it means that the test is positive and shows the presence of a certain radical. Cations are classified into the following five groups based on their behaviour against some reagents:

This classification helps to detect, identify and separate cations from the mixture of salt. So, the cation present in one group will form a similar type of precipitate. The group reagents that classify the most common cations are hydrochloric acid, hydrogen sulphide, ammonium sulphide, and ammonium carbonate.

Watch this video to learn more about chemistry.