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Ground state term ion free symbol for Na2[Co(SCN) 4]
Accepted Answer
The ground state term symbol for the complex ion [Co(SCN)₄]²⁻ is ⁴A₂. Here's how we determine it:
1. Cobalt(II) Ion (Co²⁺): Cobalt(II) has an electronic configuration of [Ar]3d⁷. In a tetrahedral complex, the d orbitals split into two sets: e (dxy, dxz, dyz) and t₂ (dx², dy²). Since the complex is tetrahedral, the e orbitals are lower in energy than the t₂ orbitals.
2. Ligand Field Splitting: Thiocyanate (SCN⁻) is a weak-field ligand, so the crystal field splitting energy (Δ) is small. This means the electrons will fill the d orbitals individually before pairing up. The electronic configuration of Co²⁺ in the complex is (t₂⁵e²) with 5 electrons in the t₂ orbitals and 2 in the e orbitals.
3. Spin Multiplicity: With 3 unpaired electrons, the spin multiplicity (2S+1) is 4 (S = 3/2). This gives us the superscript '⁴' in the term symbol.
4. Total Orbital Angular Momentum: The total orbital angular momentum (L) is determined by the sum of the individual orbital angular momenta. In this case, since we have a tetrahedral complex, the d orbitals are not degenerate and the contribution to L is zero. Therefore, the term symbol has a subscript 'A'.
5. Ground State Term Symbol: Combining the spin multiplicity and the total orbital angular momentum, the ground state term symbol for [Co(SCN)₄]²⁻ is ⁴A₂.
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