Question

Which of the following elements shows variable valency?

• A. Magnesium
• B. Zinc
• C. Iron
• D. Sodium

Answer 1

The correct option is C

Iron

Explanation for the correct option:

(c ) Iron

• Because of the involvement of unoccupied d-orbitals and electrons from the outermost and penultimate shells in the process, iron exhibit varying valency.
• Iron has the atomic number $26$. It possesses two electrons in the $4\mathrm{s}$ orbital and six in the $4\mathrm{d}$ orbital.
• To achieve stability, it loses two electrons in the $4\mathrm{s}$ orbital and therefore has $+2$ valency.
• And because half-filled orbitals are more stable, it loses one additional electron from the$\mathrm{d}$ orbital and thus has $+3$ valency.
• Hence this option is correct

Explanation for the incorrect options:

(a) Magnesium

• Magnesium has atomic number $12$.
• To achieve stability, it loses two electrons and therefore has $+2$ valency.
• Thus, this option is incorrect.

(b) Zinc

• Zinc has atomic number $30$.
• To achieve stability, it loses two electrons and therefore has $+2$ valency.
• Thus, this option is incorrect.

(d) Sodium

• Sodium has atomic number $11$.
• To achieve stability, it loses two electrons and therefore has $+1$ valency.
• Thus, this option is incorrect.

Hence the correct option is (c ) Iron