Question

The set of complex ions having the same number of unpaired electrons is

• A. \( [FeF_6]^{3-}, \, [MnCl_6]^{3-} \)
• B. \( [Co(CO_4)]^{3-}, \, [CoF_6]^{3-} \)
• C. \( [MnCl_6]^{3-}, \, [CoF_6]^{3-} \)
• D. \( [FeCl_6]^{3-}, \, [CoF_6]^{3-} \) \

Hint:

When determining the number of unpaired electrons in a complex ion, consider the metal’s oxidation state and the splitting of \( d \)-orbitals in the ligand field.

Answer 1

The Correct Option is C

To determine which complex ions have the same number of unpaired electrons, we need to analyze the electronic configurations of the metal ions and their oxidation states: 1. For \( [MnCl_6]^{3-} \): - Manganese (Mn) has an atomic number of 25. In the \( 3+ \) oxidation state, Mn has an electron configuration of \( [Ar]\, 3d^5 \). - As \( 3d^5 \) contains 5 unpaired electrons, there are 5 unpaired electrons in this complex. 2. For \( [CoF_6]^{3-} \): - Cobalt (Co) has an atomic number of 27. In the \( 3+ \) oxidation state, Co has an electron configuration of \( [Ar]\, 3d^6 \). - In an octahedral field, Co will undergo \( 3d \) orbital splitting, and in the case of the \( 3+ \) oxidation state, it will have 4 unpaired electrons. By this analysis, \( [MnCl_6]^{3-} \) and \( [CoF_6]^{3-} \) both contain the same number of unpaired electrons (5 for Mn and 5 for Co). Thus, the correct option is (3).