Naming chemical compounds

In a nutshell

Compounds are formed when atoms of different elements undergo a chemical reaction and form chemical bonds. There are five main rules when naming a compound. This lesson will go over these rules, with examples.

Rule 1

If a compound is made up of only two elements, then the compounds name will end in -ide. 

​​Example

Lithium chloride ($$LiCl$$​) is composed of only lithium and chlorine atoms.   

Rule 2

The first part of the compounds name must be the element that is furthest to the left in the periodic table. 

​​Example

Potassium iodide ($$KI$$) has potassium at the start of the name since potassium is in Group $$1$$​.

Rule 3

Compounds will end with the suffixes -ite or -ate if there are three or more elements present, and one of those elements is oxygen. 

Examples

Potassium iodate ($$KIO_3$$​) is made up of potassium, iodine and oxygen atoms.

The -ite suffix can be found in compounds like sodium sulfite ($$Na_2SO_3$$) and lithium nitrite ($$LiNO_2$$).

Rule 4 

In some instances, the name of the compound can contain prefixes which show how many atoms of a given element are present. ​

Prefixes

A prefix is a group of letters added to the start of an element. Prefixes are used to specify how many atoms of a given element are present in a molecule of a compound.

​The table below shows some of the most common prefixes.

​Examples

A carbon monoxide molecule ($$CO$$​) is composed of one carbon atom and one oxygen atom, therefore it contains the prefix mono-. 

Carbon dioxide (​$$CO_2$$​) is made up of one carbon atom bonded to two oxygen atoms, therefore it contains the prefix di-.

Carbon tetrachloride (​$$CCl_4$$​) has four chloride atoms in each molecule.

Rule 5

Acids composed of hydrogen and one other element will have a “hydro-“ prefix and an “-ic’ suffix. 

Example

Hydrochloric acid has the suffix -ic.​

Acids containing oxygen atoms can end with the suffix “-ous” or “-ic”. 

Examples

Phosphoric acid and nitrous acid.