Hypervalent Description With d Orbitals
Older models for explaining hypervalency invoked d orbitals. As of 2010, these models still appear in some beginning-level college texts; however, quantum chemical calculations suggest that d-orbital participation is negligible due to the large energy difference between the relevant p (filled) and d (empty) orbitals. Furthermore, a distinction should be made between "d orbitals" in the valence bond sense and "d functions" that are included in the QM calculation as polarization functions. The 3-center-4-electron bonding model has the advantage of dispensing with the need for d orbitals, which has led to its acceptance.
Read more about this topic: Three-center Four-electron Bond
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