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GCT
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But GCT : metals do not have molecular orbitals. So there is no question of HOMOs or LUMOs in a metal.
that's quite a statement. However, it is in direct contradiction to textbook definitions, so rather than argue endlessly about it here it is:
Band theory: ...delocalized electrons move freely through "bands" formed by overlapping molecular orbitals."
...since the number of atoms in even a small piece of magnesium is enormously large, the number of molecular orbitals they form is also very large
the band is a result of closely spaced molecular orbitals
The formation of these bands or as my text calls it molecular orbitals is from the individual atomic orbitals contributed by each metal. The same rule applies, the number of MOs must equal the number of AOs combined, this many MOs must be so close on an energy level diagram that they form a continuous band of energies. The point is that the molecular orbitals do exist within metals. In all contexts, it is appropriate to say that metals do have molecular orbitals, perhaps not so assertively, and it does not deserve emphasis...however it makes no sense to say that there are no molecular orbitals. The band theory is nothing too far out special and magical from the ordinary formation of molecular orbitals from atomic orbitals, it is merely a special case.