Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

Definition of valency of an element with examples

Answer Text:
Valency of an element:
- Refers to the number of electrons an atom loses or gains during a chemical reaction.
- Valency is also known as the combining power of an element.
Examples:
- Calcium, with electron arrangement 2.8.8.2 loses 2
electrons during chemical reactions and hence has
a valency of 2.
- Oxygen with electron arrangement 2.6 gains 2 electrons during chemical reactions and thus has a
valency of 2.
- Phosphorus with electron arrangement 2.8.5 has gains 3 electrons during chemical reactions and
hence has a valency of 3.
- Aluminium, with electron arrangement 2.8.3 loses 3 electrons during chemical reactions and hence
has a valency of 2.
Note: Some elements have variable valencies and are usually termed the transitional elements (metals)
Examples:
- Iron can have valency 2 or 3;
- Copper can have valency 1 or 2
- Lead can have valency 2 or 4.
Summary on valencies of common elements.