Answer and Explanation :
Paramagnetic are those which has unpaired electrons and diamagnetic are those in which all electrons are paired.
(a) V³⁺
The electronic configuration is -
The electrons in 3d orbital = 1 (Unpaired)
Thus, the ion is paramagnetic as the electrons are unpaired.
(b) Cd²⁺
The electronic configuration is -
The electrons in 4d orbital = 10 (paired)
Thus, the ion is diamagnetic as the electrons are paired.
(c) Co³⁺
The electronic configuration is -
The electrons in 3d orbital = 6 (Unpaired)
Thus, the ion is paramagnetic as the electrons are unpaired.
(d) Ag⁺
The electronic configuration is -
The electrons in 4d orbital = 10 (paired)
Thus, the ion is diamagnetic as the electrons are paired.