Chemical Nomenclature: Naming Inorganic Compounds

Posted on Jul 5, 2025 in Chemistry

Binary Salts: Definition and Nomenclature

Binary salts are inorganic compounds composed of two different elements, typically a metal and a nonmetal. When the nonmetal is a halogen, these compounds are specifically called halides. They can be considered the result of replacing the hydrogen (H) in a hydracid with a metal.

This general reaction illustrates their formation:

Acid + Base → Salt + Water (H₂O)

In this context, the acid is typically a hydracid, the base is a hydroxide, and the resulting compound is a binary salt.

Traditional Nomenclature

Binary salts are named using the nonmetal’s root with the suffix ‘-ide‘, followed by the metal’s name. If the metal has multiple valences, the suffixes ‘-ous‘ (for the lower valence) or ‘-ic‘ (for the higher valence) are used.

Stock Nomenclature

The nonmetal’s root with the suffix ‘-ide‘ is followed by the word ‘of’, then the metal’s name, and its oxidation state (valence) in Roman numerals in parentheses. If the metal has only one common valence, the Roman numeral is often omitted.

Systematic Nomenclature

A prefix indicating the number of nonmetal atoms is used, followed by the nonmetal’s root with the suffix ‘-ide‘. This is then followed by a prefix indicating the number of metal atoms and the metal’s name.

Examples of Binary Salt Naming

Hydroxides: Properties and Naming

Hydroxides, also known as bases, are formed by the combination of a metal cation (or a polyatomic cation like NH₄⁺) and the hydroxide anion (OH^–). As previously mentioned, they react with acids to form salts.

Traditional Nomenclature

Hydroxides are named with the term ‘hydroxide’ followed by the metal’s name. If the metal has multiple valences, the suffixes ‘-ous‘ (for the lower valence) or ‘-ic‘ (for the higher valence) are used.

Stock Nomenclature

The term ‘hydroxide’ is followed by the metal’s name and its oxidation state (valence) in Roman numerals in parentheses. If the metal has only one common valence, the Roman numeral is often omitted.

Systematic Nomenclature

A prefix indicating the number of hydroxide groups is used, followed by the term ‘hydroxide’ and the metal’s name. The prefix ‘mono-‘ is typically omitted.

Oxyacids: Formation and Naming Conventions

Oxyacids can be viewed as formed from acid oxides (anhydrides) by adding water. Typically, one molecule of H₂O is added to the anhydride. However, some elements like Phosphorus (P), Arsenic (As), Antimony (Sb), and Boron (B) can form oxyacids by adding 1, 2, or 3 molecules of water.

Similar to hydracids, oxyacids react with hydroxides or bases to form the corresponding salt, specifically an oxysalt.

Traditional Nomenclature

Oxyacids are named by changing the suffix of the corresponding anhydride. For polyhydrated acids, prefixes like meta- (1 molecule of water), pyro- or di- (2 molecules), and ortho- (3 molecules) are used. The ortho- prefix is often omitted.

Stock Nomenclature

The term ‘Acid’ is followed by a prefix indicating the number of oxygen atoms, then the nonmetal’s root with the suffix ‘-ic‘, and the nonmetal’s oxidation state in Roman numerals in parentheses.

Systematic Nomenclature

Named similarly to oxysalts (discussed later), they use a prefix indicating the number of oxygen atoms, followed by ‘oxo’, the nonmetal’s root with the suffix ‘-ate‘, and finally ‘of hydrogen’.

Examples of Oxyacid Naming