Question

Assertion (A): Transition elements have higher enthalpies of atomization.
Reason (R): Large number of unpaired electrons present in transition elements facilitate strong interatomic interaction and strong bonding between atoms.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct and (R) is not the correct explanation of (A)
• C. (A) is correct and (R) is incorrect
• D. (A) is incorrect and (R) is correct

Hint:

For transition elements, a larger number of unpaired \(d\)-electrons generally leads to stronger metallic bonding, higher enthalpy of atomization, and higher melting and boiling points.

Answer 1

The Correct Option is A

Think about what actually holds a metal lattice together, the atoms pack via metallic bonding, and the strength of that bonding depends on how many electrons each atom can contribute to the shared sea holding the lattice together.

Transition metals have partly filled d orbitals, so on top of their s electrons, they can also throw a good number of unpaired d electrons into the interatomic bonding. More electrons genuinely participating in bonding means a tighter, stronger lattice.

A tighter lattice is harder to pull apart into free gaseous atoms, and the energy needed for that separation is exactly the enthalpy of atomization, so more unpaired d electrons directly translates into a higher atomization enthalpy. This is why elements like tungsten and molybdenum, with several unpaired d electrons, have some of the highest atomization enthalpies of all metals.

Both statements are true, and the unpaired electron bonding explanation in R is precisely why transition metals show high atomization enthalpies in A.

So the correct choice is option (1).