Valencies of Some Commonly Used Elements / Ions

In science especially chemistry, chemical formula of a chemical compound is very important. While writing the chemical formula of a compound, the knowledge of correct symbols and valencies of the constituent elements / ions are required.


The combining power / capacity of an element is known as valency.

It is used to find out how the atoms of an element will combine with the atoms of another element to form a chemical compound.

In order to simplify the process of writing chemical formula, symbols with their valencies of some common elements / ions are mentioned below in tabular form –

I.            Metallic Ions :–

S. No.	Name	Symbol	Valency
1.	Sodium	Na+	1
2.	Potassium	K+
3.	Silver	Ag+
4.	Copper (I)* / Cuprous	Cu+
5.	Magnesium	Mg2+	2
6.	Calcium	Ca2+
7.	Zinc	Zn2+
8.	Barium	Ba2+
9.	Iron(II)*  / Ferrous	Fe2+
10.	Copper (II)* / Cupric	Cu2+
11.	Lead (II)*	Pb2+
12.	Mercury (II)* / Mercuric	Hg2+
13.	Aluminium	Al3+	3
14.	Iron (III)* / Ferric	Fe3+

*Some elements show more than one valency. A roman numeral shows their valency in a bracket.

II.            Non – Metallic Ions :–

S. No.	Name	Symbol	Valency
1.	Hydrogen	H+	1
2.	Hydride	H –
3.	Chloride	Cl–
4.	Bromide	Br–
5.	Iodide	I –
6.	Oxide	O2–	2
7.	Sulphide	S2–
8.	Nitride	N3–	3

III.            Polyatomic Ions :–

S. No.	Name	Symbol	Valency
1.	Ammonium	NH4+	1
2.	Hydroxide	OH –
3.	Nitrate	NO3–
4.	Hydrogen carbonate / bicarbonate	HCO3–
5.	Carbonate	CO3 2–	2
6.	Sulphate	SO4 2–
7.	Sulphite	SO3 2–
8.	Phosphate	PO4 3–	3

 Related Links  -

• Writing the chemical formula of chemical compounds : A step-by-step guide

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