Question

How will you find the valence of Chlorine, Sulphur and Magnesium?

Answer 1

Definition of valency

The atoms tend to achieve a stable electronic configuration or to have a complete octet in their outermost orbit. So, the number of electrons gained, lost or shared by an atom of an element to complete its octet is known as the valence of the element.

Calculation of valence of an element

• The valence of an element depends on the valence electrons (electrons in the outermost shell)
• For elements having valence electrons 1,2, or 3, valence equals to the number of valence electrons.
• For elements having valence electrons 4,5,6 or 7, valence is equal to the number of electrons added to complete the octet.

Valence = 8 - Number of valence electrons

Valency of Chlorine

• The chemical symbol of the element Chlorine = $\mathrm{Cl}$
• Atomic number (Z) = $17$
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\hspace{0.17em}\mathrm{M} \\ 2,8,7 \end{gathered}$$
• Valence electrons = $7$
• Valency = $8-7=1$
• 

Valency of Sulphur

• The chemical symbol of the element Sulphur = $\mathrm{S}$
• Atomic number (Z) = $16$
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 2,8,6 \end{gathered}$$
• Valence electrons = $6$
• Valency = $8-6=2$
• 

Valency of Magnesium

• The chemical symbol of the element Magnesium = $\mathrm{Mg}$
• Atomic number (Z) = $12$
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 2,8,2 \end{gathered}$$
• Valence electrons = $2$
• Valency = $2$