Valency

This is defined as the number of charges on the ions of an element or the combining power of an element. Atoms always gain or lose electrons on their outermost shell to other atoms. This is when the atoms are combining to form compounds. They exchange their valencies to make them compatible.

NB: The valency of an element is the same to the number of electrons gained or lost by an atom forming an ion.

Finding the Valency of Potassium

Potassium (19K)

Total number of electrons = 19

Number of electrons contained in the various shells

K shell = 2

L shell = 8

M shell = 8

N shell = 1

The 1 electron in the outermost shell thus N shell makes the atom unstable. Potassium can be stable by losing the 1 electron.. After losing the 1 electron, potassium becomes.

Proton number of +19

Electron number of – 18

The valency of Potassium = +19 – 18

                     Potassium = +1