Question

Define valency by taking the example of silicon.

Answer 1

Definition

Valency is defined as the number of electrons in an atom donated or received with another atom/atoms so as to complete its octet.

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 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

Example

Silicon($\mathrm{Si}$).

The atomic number of silicon = 14

No. of electrons = 14

Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 284 \end{gathered}$$

Thus, the outermost shell has 4 electrons which it can share with other atoms to complete its octet. so its valency = 4.