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

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) http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_14.gif

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)

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)

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).

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

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

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

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

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

References http://www.bbc.co.uk/schools/gcsebitesize/img/gcsechem_14.gif Chang, Raymond. Chemistry; McGraw-Hill: San Fransisco, 2007.