Q36 / 105 · NTA Abhyas (JEE Main) 2020 · Chemistry · d and f Block Elements

Which of the following arrangement does not represent the correct order of the property stated against it?

  • Correct answer
    A
    V2+<Cr2+<Mn2+<Fe2+: paramagnetic behaviour
  • B
    Sc<Ti<Cr<Mn: number of oxidation states
  • C
    Co3+<Fe3+<Cr3+<Sc3+: stability in aqueous solution
  • D
    Ni2+<Co2+<Fe2+<Mn2+: ionic size

Solution

A. V2+ has 3 unpaired electrons

Cr2+ has 4 unpaired electrons

Mn2+ has 5 unpaired electrons

Fe2+ has 4 unpaired electrons

Hence the order of paramagentic behaviour should be

V2+<Cr2+=Fe2+<Mn2+

B. Ionic size decreases from left to right in same period.

C. As per data, we have

Co 3+ | Co 2+ =1.97;  Fe 3+ | Fe 2+ =0.77;  Cr 3+ | Cr 2+ =−0.41

Sc3+ is highly stable, because it does not show +2.

D. The oxidation state increases as we go from group 3 to group 7 in same period.

Hence, the correct answer is option: 'A'.

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