Static Aspects Intemuclear Distances

Diffraction of X-rays or neutrons by crystals have provided very rich material on inter-nuclear distances R. If explicit determination of angles is not required, electron diffraction of gaseous molecules, or X-ray and neutron diffraction of vitreous materials, solutions, etc. may many times provide acceptable R values. If one asks for the distribution of distances from a given point in a gas of geometrical points, the density in a shell between R and R -1- dR is jaroportional to 4nR dR = P. This is also valid in actual compounds and alloys for very long R, but not at all for short R. Fig. 1 is a qualitative probability distribution of R values (normalized by division with P) for nuclei of a given element, or for a combination of two definite elements Zj and Zj. Contrary 

Photo-electron spectra have allowed us to speak freely about vertical (and in fortunate cases adiabatic at lower I, without vibronic co-excitation due to changed R values) ionization energies of gaseous molecules, like one has done most of this century for atoms. In spite of a certain resistance among classical physical chemists, it has been recognized that a chemical ionization energy 1 can be defined 

Entropy differences contribute to a large extent to the formation constants in aqueous solution, in particular of multidentate amines (of which ethylenediamine is the 

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