Question

Which of the following pairs represent variable valency?

• A. Calcium and iron
• B. Aluminium and copper
• C. Carbon and calcium
• D. Iron and copper

Answer 1

The correct option is D Iron and copper

Copper shows variable valency as it is a d-block element. Thus, copper forms compounds containing $C{u}^{+}$ ions or $C{u}^{++}$ ions. Copper shows valency $1$ and $2$

Iron shows variable valency, i.e., $2$ and $3$.