The correct order of $ [FeF_6]^{3-} $, $ [CoF_6]^{3-} $,$ [Ni(CO)_4] $ and $ [Ni(CN)_4]^{2-} $ complex species based on the number of unpaired electrons present is:
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The number of unpaired electrons in transition metal complexes can be determined based on the electronic configuration of the metal ion and the nature of the ligands.
To determine the correct order of the given complex species based on the number of unpaired electrons, we need to analyze each of them individually. Let's consider each complex:
\([FeF_6]^{3-}\):
Iron (\(Fe\)) in this complex is in the +3 oxidation state, i.e., \(Fe^{3+}\).
The electronic configuration of \(Fe^{3+}\) is \([Ar] \, 3d^5\).
\(F^-\) is a weak field ligand, causing high spin, which means all five electrons in the \(3d\) orbital remain unpaired.
Therefore, the number of unpaired electrons = 5.
\([CoF_6]^{3-}\):
Cobalt (\(Co\)) is in the +3 oxidation state in this complex, i.e., \(Co^{3+}\).
The electronic configuration of \(Co^{3+}\) is \([Ar] \, 3d^6\).
\(F^-\) is a weak field ligand, resulting in a high spin complex with four unpaired electrons.
Therefore, the number of unpaired electrons = 4.
\([Ni(CO)_4]\):
Nickel (\(Ni\)) is in the zero oxidation state, i.e., \(Ni^0\). The electronic configuration is \([Ar] \, 3d^8 \, 4s^2\).
The \(CO\) ligand is a strong field ligand and causes \((ni)\) to pair up electrons, resulting in no unpaired electrons.
Therefore, the number of unpaired electrons = 0.
\([Ni(CN)_4]^{2-}\):
Nickel (\(Ni\)) in this case is in the +2 oxidation state, i.e., \(Ni^{2+}\).
The electronic configuration of \(Ni^{2+}\) is \([Ar] \, 3d^8\).
\(CN^-\) is a strong field ligand leading to the pairing of electrons due to the low spin complex formation, resulting in no unpaired electrons.
Therefore, the number of unpaired electrons = 0.
Based on the number of unpaired electrons calculated above, the order is:
- Electronic configuration of each complex: - \( [FeF_6]^{3-} \): \( [Ar] 3d^5 4s^0 \). There are 5 unpaired electrons in the \( 3d \)-orbitals. - \( [CoF_6]^{3-} \): \( [Ar] 3d^6 4s^0 \). There are 4 unpaired electrons in the \( 3d \)-orbitals. - \( [Ni(CO)_4] \): \( [Ar] 3d^8 4s^2 \). The \( CO \) ligand is a strong field ligand, so the pairing of electrons leads to 0 unpaired electrons. - \( [Ni(CN)_4]^{2-} \): \( [Ar] 3d^8 4s^0 \). The \( CN \) ligand is a strong field ligand, leading to the pairing of all electrons, so there are 0 unpaired electrons. Thus, the order of the unpaired electrons is: \[ [FeF_6]^{3-}>[CoF_6]^{3-}>[Ni(CN)_4]^{2-} = [Ni(CO)_4] \]
