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EEJ MAIN Chemistry QUESTION #7159
Question 1
Which of the following sequences does not accurately reflect the trend of the property mentioned?
  • $V^{2+} < Cr^{2+} < Mn^{2+} < Fe^{2+}$: paramagnetic behavior✔️
  • $Ni^{2+} < Co^{2+} < Fe^{2+} < Mn^{2+}$: ionic size
  • $Co^{3+} < Fe^{3+} < Cr^{3+} < Sc^{3+}$: stability in aqueous solution
  • $Sc < Ti < Cr < Mn$: number of oxidation states
Correct Answer Explanation
Paramagnetic behavior depends on the number of unpaired electrons.
  • $V^{2+}$: $[Ar] 3d^{3}$ (3 unpaired)
  • $Cr^{2+}$: $[Ar] 3d^{4}$ (4 unpaired)
  • $Mn^{2+}$: $[Ar] 3d^{5}$ (5 unpaired)
  • $Fe^{2+}$: $[Ar] 3d^{6}$ (4 unpaired)
Since $Fe^{2+}$ has fewer unpaired electrons than $Mn^{2+}$, the increasing order shown in Option 1 is incorrect.