Integrated SequencePhysics Chemistry Organic Biology

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Purdue University - Crystal Field Theory
Fascinating material. Good treatment. May be a bit advanced for the MCAT, although is well suited to be the subject of a passage not necessarilly relying on specific prior knowledge but general familiarity.

  click if a link is broken

Special points of emphasis


The Chemical Bond

Coordination Chemistry

The Properties of Light

Most coordination complexes are brightly colored. The introduction of the electron pairs from approaching ligands splits the d subshell electrons of the transition metal into two subsets, one whose energy is raised by the new electrons, the other set that is commensurably lowered in energy. Crystal field splitting explains the colors of transition metal complexes, the energy of excitation between the two sets corresponding to photon energy in the visible range. When the complex absorbs a visible photon an electron transitions from the lower energy d orbitals to an excited state. Because only certain wavelengths are absorbed, the substance appears the complementary colour (if red is absorbed, green is observed).

Whether from crystalized coordination complexes or coordinated impurities, this is why many minerals are brightly colored such as malachite, turquoise, citrine, emerald, ruby or amethyst. Now that's just interesting.

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