Valency of Elements: Basics Every Student Should Know

Have you ever wondered how atoms decide who to bond with and how many bonds they can make? That’s exactly what valency helps us understand. In simple terms, valency tells us how many other atoms an element can connect with to become stable. It’s like the number of hands an atom has to hold onto other atoms.

On this page, the Article is broken down into the concept of valency in the simplest way possible, with easy steps to calculate it, and examples from elements you already know.

Table of Contents

• What Is Valency and Why Is It Important
• How to Determine the Valency of Any Element
• Valency vs Oxidation Number: Key Differences Explained
• Valency Chart of the First 30 Elements with Atomic Numbers
• Tips to Learn Concept Valency

What Is Valency and Why Is It Important?

Valency is one of the foundational concepts in chemistry. It tells us how atoms of different elements interact and combine to form molecules. Simply put, valency is the measure of an element's combining power. 

It's the number of electrons an atom either gains, loses, or shares to attain a stable electronic configuration, often resembling that of a noble gas.

Atoms are always aiming for stability, and in chemistry, that stability is often achieved when an atom has a full outer shell of electrons. This desire to become stable leads atoms to form bonds with other atoms by gaining, losing, or sharing electrons. Valency reflects how many electrons an atom needs to gain, lose, or share to complete its outer shell.

Key Points:

• Valency depends on the number of electrons in the outermost shell (valence shell).
• For metals, valency equals the number of electrons lost.
• For non-metals, valency equals the number of electrons gained or shared.

Example: Valency of Carbon

Carbon (C) has an atomic number of 6 and a valency of 4. It needs 4 more electrons to complete its outer shell, so it forms four covalent bonds.

Example compound: In methane (CH₄), carbon forms single bonds with four hydrogen atoms.

Example: Valency of Copper

Copper (Cu) shows variable valency: +1 (cuprous) and +2 (cupric), depending on the compound it forms.

Example compounds:

• Cu₂O (Copper(I) oxide) → Cu⁺
• CuSO₄ (Copper(II) sulfate) → Cu²⁺

How to Determine the Valency of Any Element

To determine the valency of an element, follow these general steps:

Step 1: Identify the Group Number (For Main Group Elements)

Group	Valency
1	1
2	2
13	3
14	4
15	3
16	2
17	1
18	0 (inert)

Step 2: Use the Octet Rule

• If an element has fewer than 4 electrons in the outer shell, it loses electrons → Positive valency
• If an element has more than 4 electrons, it gains electrons → Negative valency
• If it has 4, it can either gain or lose electrons → Variable valency (like carbon)

Valency vs Oxidation Number: Key Differences 

Though both terms are related to bonding and electron exchange, they differ in meaning and application.

Valency	Oxidation Number
Indicates the number of electrons lost/gained/shared	Indicates the effective charge of an atom
Always a positive whole number	Can be positive, negative, or zero
Used to write chemical formulas	Used in redox reactions and balancing equations

Valency Chart of the First 30 Elements with Atomic Numbers 

Here is a helpful table showing the valency of the first 30 elements in the periodic table:

Atomic No.	Element	Symbol	Valency
1	Hydrogen	H	1
2	Helium	He	0 (inert)
3	Lithium	Li	1
4	Beryllium	Be	2
5	Boron	B	3
6	Carbon	C	4
7	Nitrogen	N	3
8	Oxygen	O	2
9	Fluorine	F	1
10	Neon	Ne	0 (inert)
11	Sodium	Na	1
12	Magnesium	Mg	2
13	Aluminium	Al	3
14	Silicon	Si	4
15	Phosphorus	P	3 or 5
16	Sulphur	S	2, 4, or 6
17	Chlorine	Cl	1, 3, 5, or 7
18	Argon	Ar	0 (inert)
19	Potassium	K	1
20	Calcium	Ca	2
21	Scandium	Sc	3
22	Titanium	Ti	4
23	Vanadium	V	5
24	Chromium	Cr	2, 3, or 6
25	Manganese	Mn	2, 4, or 7
26	Iron	Fe	2 or 3
27	Cobalt	Co	2 or 3
28	Nickel	Ni	2 or 3
29	Copper	Cu	1 or 2
30	Zinc	Zn	2

Note: Some transition metals show variable valency due to their ability to use d-orbitals for bonding.