Bond valence method

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The bond valence method (not to be mistaken for the valence bond theory in quantum chemistry) is a popular method in coordination chemistry to estimate the oxidation states of atoms.

The basic idea is that the valence V of an atom is the sum of the individual bond valences v_i surrounding the atom:

$V = \sum(v_i)$

The individual bond valences in turn are calculated from the observed bond lengths.

$v_i=\exp \left( \frac {R_0-R_i} {b} \right)$

R_i is the observed bond length, R₀ is tabulated, and b is a constant, typically 0.37 Å.

[edit] Actinide oxides

It is possible by bond valence calculations ^[1] it is possible to estimate how great a contribution a given oxygen atom is making to the assumed valence of uranium. Zachariasen, J. Less Common Met., 1978, 62, 1-7. Lists the parameters to allow such calculations to be done for many of the actinides. Bond valence calculations use parameters which are estimated after examining a large number of crystal strucutres of uranium oxides (and related uranium compounds), note that the oxidation states which this method provides are only a guide which assists in the understanding of a crystal structure.

For uranium binding to oxygen the constants Ro and B are tabulated in the table below. For each oxidation state use the parameters from the table shown below.