TOPIC 7: FORMULA BONDING AND NOMENCLATURE | CHEMISTRY FORM 2
The Concept of Valence
Explain the concept of valence
Valency is the capacity of an atom to combine with one or more atoms to form a molecule or compound. Valency also refers the number of electrons that an atom can gain, lose or share in forming a chemical bond with another atom.
The valency (or combining power) depends on the number of electrons in the outermost orbit (or valency shell) involved in the formation of a chemical bond.
The number of electrons in the valency shell is never greater than 7. The outermost electronic configuration is responsible for the variability of the valency.
Some elements exhibit more than one valency, i.e., they have variable valencies. Examples of elements with variable valencies are iron (2 and 3), tin (2 and 4) and copper (1 and 2). The other elements with variable valencies are as shown in table 7.1.
Valency and Oxidation States
There is a strong correlation between valency and oxidation state. The