Equilibrium internuclear distance hydrogen molecule

To obtain an accurate assessment of the interelectronic repulsion energy of the H2 molecule it is essential to carry out calculations in which the hydrogen nuclei are a constant distance apart. The following calculations are for an internuclear distance of 74 pm for both molecules, which is the equilibrium internuclear distance in the dihydrogen molecule. 

In hydrogen fluoride the situation is different. For this molecule the ionic curve and the covalent curve are nearly coincident in the neighborhood of the equilibrium internuclear distance. In conse-... 

We may attempt to make a rough quantitative statement about the bond type in these molecules by the use of the values of their electric dipole moments. For the hydrogen halogenides only very small electric dipole moments would be expected in case that the bonds were purely covalent. For the ionic structure H+X-, on the other hand, moments approximating the product of the electronic charge and the internuclear separations would be expected. (Some reduction would result from polarization of the anion by the cation this we neglect.) In Table 3-1 are given values of the equilibrium internuclear distances r0, the electric moments er0 calculated for the ionic structure H+X , the observed values of the electric moments /, and the ratios of these to the values of er0.ls These ratios may be interpreted in a simple... 

The fact that the nuclei do not get closer together does not mean that the forces of attraction and repulsion are equal. The minimum distance is that distance where the total energy (attraction and repulsion) is most favorable. Because the molecule has some vibrational energy, the internuclear distance is not constant, but the equilibrium distance is Ra. Figure 3.2 shows how the energy of interaction between two hydrogen atoms varies with internuclear distance. 

The most simple molecule is the positive ion of the hydrogen molecule (Hj ) Its model, when we neglect the angular momentum s, is distinct from the two-centre problem only in the respect that the internuclear distance is not fixed, but vibrates around an equilibrium configuration which is also determined by the electronic configuration. Instead of each term in the two-centre problem a function of the distance r between the nuclei appears, of which the minimum determines the equilibrium configuration and the value of each of its terms transforms in the value of the terms of the separated systems. For small r the functions behave like 1/r, their distances like the distances between the terms in the case of a united nucleus. 

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