1. Transition Metal Chemistry: Crystal Field Theory
Jessica Comstock
Kata Haeberlin
Kelsey Fisher

2. Transition Metals
elements in which the d and f subshells are progressively filled
50 elements
transition elements with incomplete d subshells tend to form complex ions (Chang 935)

3. Periodic Trends (Wikipedia)
Going across a period, the valence doesn't change.
As a result, the electron being added to an atom goes to the inner shell, not outer shell, strengthening the shield.
Why are they called transition metals ?
The elements represent the successive addition of electrons to the d orbitals of the atoms. Transition metals represent the transition between group 2 and 13 elements.
(Wikipedia)

4. Properties high tensile strength high density
high melting and boiling points
often form colored compounds
solid at room temperature (except mercury)
form complex ions
often paramagnetic
(Wikipedia)

5. Oxidation States
Unlike group 1 and group 2 metals, transition element ions can have multiple stable oxidation states.
They can lose d electrons without a high energetic penalty (Wikipedia).

6. Crystal Field Theory
Developed in the 1930’s by Hans Bethe and John Hasbrouck van Vleck
Model that describes electronic structure of transition metal compounds
Accounts for
Some Magnetic Properties
Colors
Hydration Enthalpies
Spinal Structure of Transition Metals

7. Splitting
Attraction between positively charged metal cation and negatively charged electrons of the ligand
Repulsion of electrons
Splitting affected by
Nature of metal ion
Oxidation State
Arrangement of ligands around the metal ion
Nature of the ligands

8. Spectrochemical Series
Energy difference ∆ depends on
Ligands
Geometry of the complex
I− < Br− < S2− < SCN− < Cl− < NO3− < N3− < F− < OH− < C2O42− < H2O < NCS− < CH3CN < py < NH3 < en < phen < NO2− < PPh3 < CN− < CO

9. High / Low Spin Low Spin High Spin Large ∆ Strong-Field Ligand Cn-, Co
Small∆
Weak-Field Ligand
I-, Br-

10. Color Change in energy is equal to energy of the absorbed photon
Energy of absorbed photon is opposite of the color observed

11. References
Chang, Raymond. Chemistry; McGraw-Hill: San Fransisco, 2007.