Which of the following shows the least value for standard enthalpy of atomization?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Zn
The standard enthalpy of atomization (ΔₐₜH°) is the energy required to convert one mole of metal atoms in solid state to gaseous atoms (M(s) → M(g)).
Among the 3d-series transition metals:
- Zn has completely filled 3d¹⁰ 4s² electronic configuration.
- It has no unpaired electrons → very weak metallic bonding (almost no d-d overlap).
- As a result, zinc has the weakest metallic bond in the 3d series.
Trend in 3d series:
V > Cr > Mn > Fe > Co > Ni > Cu > Zn (lowest)
Cu has high value due to strong metallic bonding + contribution from d-electrons, but Zn shows the lowest atomization enthalpy.