Question

Define valency by taking example of Silicon and Oxygen.

Answer 1

Definition

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

Calculation of valency

• Valency of an element depends on the number of valence electrons.
• For elements having valence electrons 1,2 or 3 ,valence is equal to the number of valence electrons
• For elements having valence electrons 4,5,6 or 7 ,valence equal to the number of electrons to be added to complete the octet.

Valence = 8 - valence electrons

Oxygen

• Chemical symbol element Oxygen = $\mathrm{O}$

• Atomic number of Oxygen = 8
• No. of electrons = 8
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L} \\ 26 \end{gathered}$$
• Valence electrons = $6$
• Hence the valency = $8-6=2$

Silicon

• Chemical symbol element Silicon = $\mathrm{Si}$

• Atomic number of Silicon= 14
• No. of electrons = 14
• Electronic configuration = $$\begin{gathered} \mathrm{K}\mathrm{L}\mathrm{M} \\ 284 \end{gathered}$$
• Valence electrons = $4$
• Hence the valency = $8-4=4$