Question

Define valence electrons.

Answer 1

Valence electrons:

1. In an atom, electrons revolve in different shells.
2. The electrons present in the outermost shell (valance shell) of an atom are called valence electrons.

Example:

1. Consider Magnesium $\left(\mathrm{Mg}\right)$ atom having atomic atomic number $12$.
2. Electronic configuration of Magnesium is $(2,8,2)$.
3. There are $2$ electrons in the outermost shell.
4. Thus, the number of valence electrons in Magnesium is $2$.