Question

Which among the following pairs of elements is 'not' an example of chemical twins?

• A. $Zr$ and $Hf$
• B. $Nb$ and $Ta$
• C. $Mo$ and $W$
• D. $Ta$ and $Re$

Answer 1

The correct option is D $Ta$ and $Re$

A pair of elements having similar properties due to similar atomic radii are called chemical twins and they are elements of $4d$ and $5d$ series respectively. Out of the given pairs, $Ta$ and $Re$ are not the example of chemical twins because they have a large difference in their atomic radii while all other elements have almost similar atomic radii.

$Zr\left(145pm\right)$ and $Hf\left(144pm\right)$

$Nb\left(134pm\right)$ and $Ta\left(134pm\right)$

$Mo\left(129pm\right)$ and $W\left(130pm\right)$

$Ta\left(134pm\right)$ and $Re\left(114pm\right)$.