Titanium fill chloride

In the sodium chloride structure, the symmetry enables three of the five d orbitals on different atoms to overlap. Because the atoms are not nearest neighbours, the overlap is not as large as in pure metals and the bands are thus narrow. The other two d orbitals overlap with orbitals on the adjacent oxygens. Thus, two narrow 3c/ bands exist. The lower one, labelled 2g. can take up to 67Velectrons, and the upper one, labelled 6g, up to 47V electrons. Divalent titanium has two d electrons, therefore, 27V electrons fill the 37V levels of the lower band. Similarly, divalent vanadium has three d electrons and so the lower band is half full. As in the case of pure metals, a partly filled band leads to metallic conductivity. For FeO, the /2g band would be full, so it is not surprising to find that it is a semiconductor but MnO with only five electrons per manganese is also a semiconductor. 

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