Question

Define valency

Answer 1

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 valency of the element.
• Valency of an element depends on the valance of electrons.
• If the valence electrons of an element are equal to 1,2, or 3, then valency equals the number of valence electrons.
• If the element has valence electrons 4,5,6, or 7, then valency is equal to the number of electrons to be added to complete the octet.

valency = 8 - valence electrons.

• For noble gas valency is zero as they have fully filled orbitals.

Example

• The chemical symbol of the element $\mathrm{Sodium}=\mathrm{Na}$
• Atomic number of $\mathrm{Sodium}=11$
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 281 \end{gathered}$$
• Valence electrons = $1$
• Therefore valency of $\mathrm{Sodium}\left(\mathrm{Na}\right)=1$