Which of the following is NOT correctly matched?
A. Element of 1st transition series with highest 2nd ionization enthalpy: Cu
B. Element of 1st transition series with the lowest atomization: Zn
C. Last element of 2nd transition series: Hg
D. Element of the 1st transition series with highest 3rd ionization enthalpy: Zn
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → C only
The second transition series (4d series) runs from Y to Cd; Hg is the last element of the third (5d) series.
(A) Element of 1st transition series with highest 2nd ionization enthalpy: Cu — Correctly matched. Cu (Z = 29) is [Ar] 3d10 4s1; removing 4s1 gives \( \ce{Cu+} \), 3d10. The second electron has to come out of this completely filled d10 set, so Cu has the highest second ionisation enthalpy (1958 kJ mol−1).
(B) Element of 1st transition series with the lowest atomization: Zn — Correctly matched. Zn (Z = 30) is [Ar] 3d10 4s2; it has no unpaired d electrons for metallic bonding, so its enthalpy of atomisation is the lowest of the series.
(C) Last element of 2nd transition series: Hg — Not correctly matched. The 4d series ends with Cd (Z = 48).
(D) Element of the 1st transition series with highest 3rd ionization enthalpy: Zn — Correctly matched. \( \ce{Zn^2+} \) is 3d10; the third electron has to come out of a filled d10 set, giving the highest third ionisation enthalpy (3833 kJ mol−1).
NCERT (2026-27 edition):
The d- and f-Block Elements – …
