How to Name Compounds in Inorganic Chemistry

The naming of compounds otherwise known as the nomenclature of compounds follows a standard method of nomenclature called the International Union of Pure and Applied Chemistry (IUPAC).

Though the British curriculum and IGCSE exam still accept British nomenclature and equally IUPAC nomenclature, so it is important you know the two nomenclatures.

I will start by explaining the British nomenclature and then down to the IUPAC nomenclature.

I will like you to know how the radicals are named;

Must Know/s in Nomenclature of Compounds

   SO₄^2- is called sulfate

   CO₃^2- is called carbonates

   NO₃^– is called nitrates

   MnO₄^– is called mangannate

Examples

CaCO₃   is called Calcium Carbonate

You need to name the metal first i.e cations

Similarly

K₂CO₃ is called Potassium Carbonate

MgCO₃ is Magnesium Carbonate

CuCO₃ is Copper II carbonate

PbCO₃ is Lead II carbonate

Do you know why in the last two compounds, I had to mention the valency of the metals?

It is because the metals are transition metals and you need to mention the valency i.e the state of the metal in the compound. This is crucial because transition metals have variable oxidation states.

I talked about this in balancing chemical equations and forming compounds by exchange of valencies.

I will love to talk about the IUPAC nomenclature of these compounds but please I need to emphasize that learning how to name compounds in organic chemistry is different from naming compounds in inorganic chemistry.

There are simple steps required in naming compounds in inorganic chemistry and this post will combine both namings of compounds using IUPAC nomenclature and British nomenclature. However, this is not about the naming of compounds in organic chemistry.

Steps required in naming compounds in inorganic chemistry-IUPAC nomenclature

1. When naming compounds, start with metallic ion or ammonium ion

E.g NaCl –Sodium Chloride  KBr-Potassium Bromide

2. When naming Binary compounds, the compound should nd with the second element.

However, the second element should end with –ide.

            E.g oxygen ends with oxide, fluorine ends with fluoride, chlorine with chloride, etc

            NaBr – Sodium bromide, KCl-Potassium Chloride, MgI₂-Magnesium iodide

            Have you wondered how we form the compounds? No worries, I did a full post on how to form the

formulae of compounds.

3. When naming compounds containing three elements, you need to name the first element first, last or third element, and middle element last.

But you will need to determine the oxidation state of the middle element before you can properly name the compound.

Take a look at some examples

            CaCO₃

            British nomenclature says Calcium Carbonate

            IUPAC nomenclature says otherwise

            Calcium trioxocarbonate IV

            But how did we deduce the oxidation state.

            Take a look

Nomenclature of compounds of some compounds

Other Examples

Example 1

K₂CO₃ 

You need to calculate the oxidation state of carbon.

Using the valencies of other elements except for Carbon

  2(1) + C + 3(-2) = 0

  2 + C- 6 = 0

  C = 6-2 =4

IUPAC name is Potassium trioxocarbonate IV

British name is Potassium carbonate

Example 2

Ca(NO₃)₂

 2 + 2N + 6(-2) = 0

 2 + 2N -12 =0

 2N = 12-2 =10

  N = 10/2

  N =5

IUPAC nomenclature is Calcium trioxonitrate V

British name is Calcium nitrate

Example 3

Na₂SO₄

IUPAC nomenclature is Sodium tetraoxosulphate VI

British nomenclature is Sodium sulfate

Example 4

CO

Recall that we need to calculate the oxidation of carbon first before naming the compound in IUPAC Nomenclature

IUPAC nomenclature is Carbon II oxide

British nomenclature is carbon monoxide

Example 5

CO₂

IUPAC Nomenclature is Carbon IV oxide

British nomenclature is carbon dioxide

Example 6

CuO

Please take note of the compounds of transition metals; you need to mention the state or valency of the transition metals. 

IUPAC Nomenclature is copper II oxide

British nomenclature is cupric oxide

Example 7

Cu₂O

IUPAC Nomenclature is Copper I oxide

British nomenclature is cuprous oxide

Example 8

FeCl₂

IUPAC Nomenclature is iron II chloride

British nomenclature is Ferrous chloride

Example 9

FeCl₃

IUPAC Nomenclature is iron III chloride

British nomenclature Ferric chloride

Example 10

Please note that naming binary compounds is very easy

MgCl₂ is Magnesium Chloride

KCl is potassium chloride

CaO is Calcium oxide

MgO is Magnesium oxide

AgBr is Silver bromide

CaI₂ is Calcium iodide

In conclusion, it is important I emphasize this again; nomenclature of compounds in inorganic chemistry is different from naming compounds in organic chemistry.