Question

What is the meaning valency?

Answer 1

1. Valency of an element is defined as the electrons present in the outermost shell of an atom.
2. In an atom the electrons present in the outermost shell may combine with other atoms.
3. Valency is also defined as the number of electrons lost or gained in an atom.
4. In order to understand the valency of an atom, take an example of a Magnesium$\left(\mathrm{Mg}\right)$ element.
5. The electronic configuration of Magnesium is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^2$.
6. The last electrons fill in the s-subshell.
7. The valence shell contains 2 electrons in its outermost shell.
8. To attain the stable noble gas configuration the atom will lose two electrons and therefore the valency of Magnesium is 2.