Verified Solution • 2025–26 Session moderate

QAIPMT-2007-Ch-2300: NEET 2007 Chemistry - Class 12 AIPMT-2007-Ch-2300 Solution: The d electron configurations of \(Cr^{2+}\), \(Mn^{2+}\),…

The d electron configurations of Cr2+Cr^{2+}, Mn2+Mn^{2+}, Fe2+Fe^{2+} and Ni2+Ni^{2+} are 3d43d^4, 3d53d^5, 3d63d^6 and 3d83d^8 respectively. Which one of the following aqua complexes will exhibit the minimum paramagnetic behaviour? (At. No. Cr = 24, Mn = 25, Fe = 26, Ni = 28)

Multiple Choice Options

  • A [Fe(H2O)6]2+[Fe(H_2O)_6]^{2+}
  • B [Ni(H2O)6]2+[Ni(H_2O)_6]^{2+}
  • C [Cr(H2O)6]2+[Cr(H_2O)_6]^{2+}
  • D [Mn(H2O)6]2+[Mn(H_2O)_6]^{2+}

Step-by-Step Verified Solution

Cr 2+ = 3d 4 (4 unpaired electrons) Mn 2+ = 3d 5 (5 unpaired electrons) Fe 2+ = 3d 6 (4 unpaired electrons) Ni 2+ = 3d 8 (2 unpaired electrons) Thus, [Ni(H 2 O) 6 ] 2+ exhibit minimum paramagnetic behaviour. Greater the number of unpaired electrons, higher is the paramagnetism. Hence Ni 2+ will exhibit the minimum paramagnetic behaviour.

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