Which one of the following will exhibit maximum paramagnetic character?
Answer & explanation
Correct answer: option 4
The correct answer is option 4. \([Mn(H_2O)_6]^{2+}\).
The paramagnetic character of a transition metal complex is determined by the presence of unpaired electrons in the metal's d orbitals. More unpaired electrons result in higher paramagnetic character. Let's examine each complex in detail:
1. \([Fe(H_2O)_6]^{2+}\):
Iron (Fe) in the +2 oxidation state has an electronic configuration of \([Ar] 3d^6\). In this complex, all six ligands are water molecules, and they form coordinate bonds with iron. The \(3d\) orbital can accommodate a total of 10 electrons. Since \(Fe^{2+}\) has 6 electrons in the \(3d\) orbital, there are 4 unpaired electrons.
2. \([Cr(H_2O)_6]^{2+}\):
Chromium (Cr) in the +2 oxidation state has an electronic configuration of \([Ar] 3d^4\). In this complex, all six ligands are water molecules. There are 4 unpaired electrons in the \(3d\) orbital of chromium.
3. \([Co(H_2O)_6]^{2+}\):
Cobalt (Co) in the +2 oxidation state has an electronic configuration of \([Ar] 3d^7\). In this complex, all six ligands are water molecules. There are 3 unpaired electrons in the \(3d\) orbital of cobalt.
4. \([Mn(H_2O)_6]^{2+}\):
Manganese (Mn) in the +2 oxidation state has an electronic configuration of \([Ar] 3d^5\). In this complex, all six ligands are water molecules. There are 5 unpaired electrons in the \(3d\) orbital of manganese.
Comparison of Unpaired Electrons:
\([Fe(H_2O)_6]^{2+}\): 4 unpaired electrons
\([Cr(H_2O)_6]^{2+}\): 4 unpaired electrons
\([Co(H_2O)_6]^{2+}\): 3 unpaired electrons
\([Mn(H_2O)_6]^{2+}\): 5 unpaired electrons
Therefore, the complex with the maximum paramagnetic character is \([Mn(H_2O)_6]^{2+}\) as it has the highest number of unpaired electrons (5).