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General Chemistry Principles, Patterns, and Applications, 2011

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Figure 23.16 The Jahn–Teller Effect<br />

Increasing the axial metal–lig<strong>and</strong> distances in an octahedral d 9 complex is an example of a Jahn–<br />

Teller distortion, which causes the degenerate pair of eg orbitals to split in energy by an<br />

amount δ1; δ1 <strong>and</strong> δ2 are much smaller than Δo. As a result, the distorted system is more stable<br />

(lower in energy) than the undistorted complex byδ1/2.<br />

Thermodynamic Effects<br />

As we previously noted, CFSEs can be as large as several hundred kilojoules per mole, which is the same<br />

magnitude as the strength of many chemical bonds or the energy change in most chemical reactions.<br />

Consequently, CFSEs are important factors in determining the magnitude of hydration energies, lattice<br />

energies, <strong>and</strong> other thermodynamic properties of the transition metals.<br />

Hydration Energies<br />

The hydration energy of a metal ion is defined as the change in enthalpy for the following reaction:<br />

Equation 23.12<br />

M 2+ (g) + H 2 O(l) → M 2+ (aq)<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

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