Overlap interaction ionic compounds

MO models may be used for molecules that have covalent bonds. Ionic bonds having little orbital overlap between the bonded atoms are less influenced by the stereochemical guidance of the valence orbitals. The geometry of ionic compounds is mainly determined by the electronic repulsion between the nonbonded atoms. A bonding model that considers the latter interaction as the dominant factor for determining molecular geometries is the VSEPR approach, which is discussed further below. 

In general, overlap of incompletely filled p orbitals results in large deviations from pure ionic bonding, and covalent interactions result. Incompletely filled / orbitals are usually well shielded from the crystal field and behave as essentially spherical orbitals. Incompletely filled d orbitals, on the other hand, have a large effect on the energetics of transition metal compounds and here the so-called crystal field effects become important. 

Fe +/Fe + couple is at 2.8—3.5 V in these struc-tures °), namely, the so-called inductive effect of the phosphate groups. The covalent P—O bonds of the phosphate groups will presumably increase the ionic character of the Li—O and M—O bonds in these compounds,reducing the extent of overlap and thus hyperfine interactions in these materials. 

Another difference is that the 5/ orbitals have a greater spatial extension relative to the 6,s and 6

electron-spin resonance spectrum of UF3 in a CaF2 lattice shows structure attributable to the interaction of fluorine nuclei and the electron spin of the U3+ ion. This implies a small overlap of 5/ orbitals with fluorine and constitutes an/covalent contribution to the ionic bonding. With the neodymium ion a similar effect is not observed. Because they occupy inner orbitals the 4/ electrons in the lanthanides are not accessible for bonding purposes and virtually no compound in which 4f orbitals are used can be said to exist. 

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