Chemistry Transition Elements BUMHS 2022
PMDC Verified Question 33 of 68
Which pair of ions have five unpaired d-electrons?
A
\( Fe^{+2} \) and \( Mn^{+2} \)
B
\( Fe^{+2} \) and \( Mn^{+3} \)
C
\( Fe^{+3} \) and \( Mn^{+3} \)
D
\( Fe^{+3} \) and \( Mn^{+2} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \( Fe^{+3} \) and \( Mn^{+2} \)
Concept:

We must evaluate the electron configuration of each ion to find the pair where both possess exactly a \(3d^5\) configuration.

Solution:

  • \(Mn\) (Z=25): Neutral is \([Ar] \; 3d^5 \; 4s^2\).
    For \(Mn^{2+}\), remove two \(4s\) electrons \(\implies 3d^5\) (5 unpaired).


  • \(Fe\) (Z=26): Neutral is \([Ar] \; 3d^6 \; 4s^2\).
    For \(Fe^{3+}\), remove two \(4s\) electrons and one \(3d\) electron \(\implies 3d^5\) (5 unpaired).


  • Therefore, both \(Fe^{3+}\) and \(Mn^{2+}\) have exactly 5 unpaired d-electrons.


Why other options are incorrect:

  • \(Fe^{2+}\) is \(3d^6\) (4 unpaired electrons).


  • \(Mn^{3+}\) is \(3d^4\) (4 unpaired electrons).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

Previous Question All Transition Elements MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App