Textbook Question
Draw a crystal field energy-level diagram for the 3d orbitals of titanium in [Ti(H2O)6]3+]. Indicate the crystal field splitting, and explain why is [Ti(H2O)6]3+] colored.
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24. Transition Metals and Coordination Compounds
Crystal Field Theory: Octahedral Complexes
Multiple Choice
In crystal field theory, what is the maximum number of unpaired electrons possible in an octahedral complex?
A
6
B
4
C
3
D
5
Verified step by step guidance1
Understand that in crystal field theory, the number of unpaired electrons depends on the metal ion's d-electron configuration and the strength of the ligand field in an octahedral complex.
Recall that an octahedral crystal field splits the five degenerate d orbitals into two sets: the lower-energy t\_2g orbitals (three orbitals) and the higher-energy e\_g orbitals (two orbitals).
Consider the case of a weak field ligand where the crystal field splitting energy (\$\(\Delta\)_\{oct\}\$) is small compared to the pairing energy, so electrons occupy orbitals to maximize unpaired electrons (high-spin configuration).
For a d\$^6\$ metal ion in a high-spin octahedral field, electrons fill the t\_2g and e\_g orbitals singly before pairing, resulting in the maximum number of unpaired electrons.
Count the maximum number of unpaired electrons by placing one electron in each of the five d orbitals first, then adding the sixth electron paired in one of the orbitals, leading to a maximum of 4 unpaired electrons in this example; however, for d\$^5\$ high-spin, the maximum is 5 unpaired electrons, and for d\$^0\$ to d\$^4\$ configurations, the maximum varies accordingly, with the absolute maximum being 6 unpaired electrons for a d\$^6\$ high-spin complex with appropriate electron configuration.
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