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JEE Main 20253 AprilMorning Shift
Exam
JEE Main
Year
2025
Date
3 April
Shift
Morning Shift
Subject
Chemistry
Chapter
d and f Block Elements

JEE Main 2025 · 3 April · Morning Shift · Chemistry · d and f Block Elements

The metal ions that have the calculated spin only magnetic moment...

The metal ions that have the calculated spin only magnetic moment value of 4.9 B.M. are
A. Cr2+\mathrm{Cr}^{2+}
B. Fe2+\mathrm{Fe}^{2+}
C. Fe3+\mathrm{Fe}^{3+}
D. Co2+\mathrm{Co}^{2+}
E. Mn3+\mathrm{Mn}^{3+}
Choose the correct answer from the options given below

Options

  1. AA, C and E only
  2. BA, D and E only
  3. CB and E only
  4. DA, B and E only

Correct answer

D. A, B and E only

Step-by-step solution

Given magnetic moment =4.9=4.9 B.M.
We know M.M =n(n+2)=\sqrt{\mathrm{n}(\mathrm{n}+2)} B.M.
Where, n→\mathrm{n} \rightarrow No. of unpaired e−\mathrm{e}^{-}
4.9=n(n+2)4.9=\sqrt{\mathrm{n}(\mathrm{n}+2)}
We get n=4\mathrm{n}=4
(A) 24Cr2+⇒[Ar]3 d4{ }_{24} \mathrm{Cr}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^4 (4 unpaired e)
(B) 26Fe2+⇒[Ar]3 d6{ }_{26} \mathrm{Fe}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^6 (4 unpaired e)
(C) 26Fe3+⇒[Ar]3 d5{ }_{26} \mathrm{Fe}^{3+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^5 (5 unpaired e)
(D) 27Co2+⇒[Ar]3 d7{ }_{27} \mathrm{Co}^{2+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^7 (3 unpaired e−\mathrm{e}^{-})
(E) 25Mn3+⇒[Ar]3 d4(4{ }_{25} \mathrm{Mn}^{3+} \Rightarrow[\mathrm{Ar}] 3 \mathrm{~d}^4 \quad\left(4\right. unpaired \left.\mathrm{e}^{-}\right)
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