Due to lanthanide contraction following pair(s) may have approximately equal size:

Due to lanthanide contraction following pair(s) may have approximately equal size:
  1. $\mathrm{Zr}$ and $\mathrm{Hf}$
  2. $\mathrm{Nb}$ and $\mathrm{Ta}$
  3. $\mathrm{Mo}$ and $\mathrm{W}$
  4. all of these

Solution

Because of lanthanoid contraction, $\mathrm{Zr}(40)$ and $\mathrm{Hf}(72)$ have nearly the same atomic radii.\n$\begin{array}{cc} \text{Element} & \text{ Radius (ppm) } \\\mathrm{Zr}(40) & 145 \\\mathrm{Hf}(72) & 144 \\\mathrm{Ta}(73) & 134 \\\mathrm{Ti}(22) & 132 \\\mathrm{Nb}(41) & 134\end{array}$

Asked in: JEE-TOPICTESTS-CHEMISTRY

Practice more THE D AND F BLOCK ELEMENTS questions on Aicharya