Octet expansion

The octet expansion describes an expansion of the classic octet rule . The octet rule says that many atoms form molecules or ions in which the number of outer electrons ( valence electrons ) of the atoms is eight. However, the octet rule only applies strictly to the elements of the 2nd period .

With the octet rule, the s and p orbitals of the individual atoms are filled or emptied, with the respective atoms adopting the noble gas configuration. However, if an atom of an element is present in the molecule which also contains empty d orbitals of the same shell, it was assumed until recently that valence electrons of the binding partners could also fill these orbitals. As we know from recent quantum mechanical investigations, the element has more than eight valence electrons and no longer fulfills the octet rule , not as a result, but for other reasons (see for example multi-center bond ). Since this expansion of the octet state also leads to stable connections, one speaks here of the phenomenon of octet expansion.

literature

• Kurt Peter C. Vollhardt, Neil Eric Schore: Organic Chemistry . 5th edition. John Wiley & Sons, 2011, p. 17 ( Google Books ).