The ions which contain unpaired electrons exhibit paramagnetic behaviour.
The electronic configuration of the ions are given below:
\(Ti ^{3+}=1 s ^{2} 2 s ^{2} 2 p ^{6} 3 s ^{2} 3 p ^{5}\)
\(Cu ^{2+}=1 s ^{2} 2 s ^{2} 2 p ^{6} 3 s ^{2} 3 p ^{5} 3 d ^{9}\)
\(Mn ^{3+}=1 s ^{2} 2 s ^{2} 2 p ^{6} 3 s ^{2} 3 p ^{5} 3 d ^{4}\)
Thus, all of them have unpaired electrons. Hence, they will show paramagnetic behaviour.
In option (B) \(V ^{3+}\) does not possess any unpaired electrons.
In option (C) \(Zn ^{2+}\) does not possess any unpaired electrons.
Similarly, in option (D) \(Zn ^{2+}\) does not possess any unpaired electrons.
So, the correct option is (C): \(Ti^{3+}, Cu^{2+} , Mn^{3+}\)
The elements, in the columns of the periodic table in which d subshells are being occupied are known as d block elements.
These are the elements that have the capability of forming stable cations with incompletely filled d orbitals. Elements like mercury and Zinc are not considered transition metals because they have electronic configurations: (n-1)d10 ns2. These elements have filled d-orbitals in their ground state and, therefore, even in some of their oxidation states.