Which cation from following exhibits no magnetic moment?

Step-by-step solution

The cation with zero magnetic moment is the one possessing no unpaired electrons, as the magnetic moment is given by n(n+2) BM, becoming zero when n = 0 . Electronic configurations and unpaired electrons: For Cr ³⁺ : [ Ar ] 3d^3 ( n = 3 ). For Sc ³⁺ : [ Ar ] 3d^0 ( n = 0 ). For Cu ²⁺ : [ Ar ] 3d^9 ( n = 1 ). For V ³⁺ : [ Ar ] 3d^2 ( n = 2 ). Only Sc ³⁺ has no unpaired electrons, so its magnetic moment is zero.