An element’s combining capacity is known as its valency.
The valency of the element represents the number of bonds that an atom can form as part of a compound.
How to find the valency of an element:
The valency of an element depends on the electrons present in the outermost shell, that is, valence electrons.
An element always tries to attain stability by gaining or losing electrons to obtain the octet (8 electrons in the outermost shell). So the number of valence electrons can vary from 1 to 8.
If the valence electrons of the element vary from 1 to 4. Then, the valence of electrons itself is their valency.
If the valence electrons are more than 4, subtract the number of valence electrons from the 8 (octet).
Example:
Sodium (Na) has a total of 11 electrons since its atomic number is 11.
Electronic configuration of Na is .
It will one electron to attain stable electronic configuration.