Discussion Forum



1)

Which of the following arrangements does not represent the correct order of the property stated against it"


A) $V^{2+}$ < $Cr^{2+}$ < $Mn^{2+}$ < $Fe^{2+}$: paramagnetic behaviour

B) $Ni^{2+}$ < $Co^{2+}$ < $Pe^{2+}$ < $Mn^{2+}$ : ionic size

C) $Co^{3+}$ < $Fe^{3+}$ < $Cr^{3+}$ < $Sc^{3+}$: stability in aqueous solution

D) Sc < Ti < Cr < Mn : number of oxidation states

Answer:

Option A

Explanation:

(a)   $V^{2+}$  = 3 unpaired elecrons

  $Cr^{2+}$  = 4 unpaired electrons

 $Mn^{2+}$  = unpaired electrons

  $Fe^{2+}$= 4 unpaired electrons

 Hence, the order of paramagnetic behaviour should be

 $V^{2+}$  < $Cr^{2+}$=   $Fe^{2+}$ <   $Mn^{2+}$

(b) ionic size decreases from left to right in the same period

 (c) $Co^{3+}$/   $Co^{2+}$= 1.97

  $Fe^{3+}$/  $Fe^{2+}$ = 0.77

  $Cr^{3+}$/  $Cr^{2+}$= -.041

   $Sc^{3+}$ is highly stable ( it does not show +2)

(d) The oxidation  states increases as we go from group 3 to group 7 in the same period