Which of the following arrangements does not represent the correct order of the property stated against it ?A. `Sc ltTi lt Cr lt Mn :` number of oxidation statesB. `V^(2+) ltCr^(2+) lt Mn^(2+) lt Fe^(2+) :` paramagnetic behaviourC. `Ni^(2+) lt Co^(2+) lt Fe^(2+) lt Mn^(2+) :` ionic sizeD. `Co^(3+) lt Fe^(3+) lt Cr^(3+) lt Sc^(3+) :` stability in aqueous solution.

Which of the following arrangements does not represent the correct ord

1.	Which of the following arrangements does not represent the correct order of the property stated against it ?A. `Sc ltTi lt Cr lt Mn :` number of oxidation statesB. `V^(2+) ltCr^(2+) lt Mn^(2+) lt Fe^(2+) :` paramagnetic behaviourC. `Ni^(2+) lt Co^(2+) lt Fe^(2+) lt Mn^(2+) :` ionic sizeD. `Co^(3+) lt Fe^(3+) lt Cr^(3+) lt Sc^(3+) :` stability in aqueous solution.
Answer» (a) Number of oxidation states increases along a period.Hence, (a) is correct. (b) `V=3d^(3) 4s^(2) , V^(2+) = 3d^(3)= 3` unpaired `e^(-)` `Cr= 3d^(5) 4s^(1) , Cr^(2+)= 3d^(4) = 4` unpaired `e^(-)` `Mn= 3d^(5)4s^(2), Mn^(2+)= 3d^(2+)= 5` unpaired `e^(-)` `Fe=3d^(6) 4s^(2), Fe^(2+)= 3d^(6) = 4` unpaired`e^(-)` Hence, correct order of paramagnetic behaviour will be `V^(2+) lt Cr^(2+) = Fe^(2) lt Mn^(2+)`. Thus, `(b)` is incorrect.(c ) Ionic radii `(M^(2+))` increase along the period . Hence, (c ) is correct. (d) Stability of `M^(3+)` ion is aqueous soltuion increases as `E_(M^(3+) //M^(2+))^(@)` values decrease. Hence, (d) is correct