Ionic Triatomic Molecules The Alkaline Earth Halides

Molecule Ground state Bond Bond length, A Bond energies, kcal/mole 

Our purpose is to calculate the average Ca—Cl bond energy in CaCh  

The energy per bond is one-half —3.5 /R, or — 1.75eVR- The van der Waals energy can be approximated again as an inert-gas-pair interaction. In this case we have one Ar-Ar interaction for each bond. The inert-gas-pair approximation of the van der Waals energy is not expected to be as good for the MX molecules as for the 

MX molecules, however, owing to the small size of M compared to that of the isoelecttonic inert gas atoms (see Fig, 3-13). Thus the actual Ca —Cl van der Waals repulsion energy is probably less than that calculated. 

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