Question

Assertion : The number of unpaired electrons in the following gaseous ions:
`Mn^(3+), Cr^(3+), V^(3+)` and `Ti^(3+)` are 4,3,3 and 1 respcetively.
Reason : `Cr^(3+)` is most stable in aqueous solution amongst these ions
A. If both assetion and reason are true and the reason is the correct explanation of the assertion.
B. If both assertion and reason are ture but reason is not the correct explanation of the assertion.
C. If assertion is true but reason is false.
D. If assertion is false but reason is true.

Answer 1

Correct Answer - B
Assertion : `Mn^(3+) = [Ar]^(18) 3d^(4)`, so `n = 4 , Cr^(3+) = [Ar]^(18) 3d^(3)`, so `n = 3 , V^(3+) = [Ar]^(18) 3 d^(2)` , so `n = 2, Ti^(+3) = [Ar]^(18) 3d^(1)`, so `n = 1`.
Reason : `Cr^(3+)` is most stable accroding to `CFSE` (half-filled t2g) configuration gives higher `CFSE` value `3 xx 0.4 = 1.2 Delta p` in octahedral spliting in presenece of ligands.