Question

Valency of oxygen is generally two whereas sulfur shows valency of two four and six. Explain.

Answer 1

Valency:

• “Valency is the combining capacity of an atom.”
• “The electrons present in the outermost shell of an atom are known as the valence electrons.”

Valency of Oxygen:

• Oxygen is a chemical element with an atomic number $8$.
• The electronic configuration of Oxygen is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^4$.
• It has six valence electrons.
• Thus, the valency for the oxygen atom is $2$ as it requires two more electrons to complete its octet.

Valency of sulfur:

• Sulfur is a chemical element with an atomic number $16$.
• The electronic configuration of Sulfur is $1{\mathrm{s}}^{2}2{\mathrm{s}}^{2}2{\mathrm{p}}^{6}3{\mathrm{s}}^{2}3{\mathrm{p}}^4$.
• It has six valence electrons.
• Sulfur shows valencies of two, four, and six due to the presence of the empty d-orbital.
• It has a valency of $2$ as it only requires two more electrons to complete its octet.
• It can either make four orbitals singly occupied or six orbitals singly occupied showing valency $4$ or $6$.