Naming Chemicals

The names given to chemical compounds follow some general rules. We will look at some basic rules.



Naming Ionic Compounds

1. When naming an ionic compound, the metallic element comes before the non-metallic element and the non-metallic element ends with “ide”

The following table shows some examples:

Elements in an ionic compound

Chemical name

Calcium, chlorine

Calcium chloride

Iodine, lithium

Lithium iodide

Magnesium, Oxygen

Magnesium oxide

Sulfur, potassium

Potassium sulfide

2. In an ionic compound which contains a transition metal, a Roman numeral in a bracket is generally assigned to indicate the valency.

For example:

Iron(II) oxide and iron(III) oxide

Copper(I) oxide and copper(II) oxide

Lead(II) oxide and lead(IV) oxide

3. A polyatomic ion will not change its name after combining with other elements

For example:

Sodium Carbonate

Potassium Sulfate



Naming covalent compounds

When naming a covalent compound, the name of the first element is unchanged, the name of the second element ends with “ide” and if necessary, a prefix is used for the second element to indicate the number of atoms involved.

For example:

Carbon with one oxygen atom – carbon monoxide (CO)

Carbon with two oxygen atoms – carbon dioxide (CO2)

Sulfur with three oxygen atoms – sulfur trioxide (SO3)

Carbon with four chlorine atoms – carbon tetrachloride (CCl4)


Certain covalent compounds have “common” names.

For example:

Water – H2O

Ammonia - NH3




Name the following substances:

a) MgCl2

b) Fe2(CO3)3

c) NH4OH


a) Magnesium Chloride

b) Iron(III) Carbonate

c) Ammonium Hydroxide



The following videos show the naming of some compounds




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