Sulfur hexafluoride valence shells

Sulfur hexafluoride Oh). Six sulfur-fluorine cr bonds require 2 electrons in the valence shell. Six equivalent bonds require an octahedron and so sulfur wjU be hybridized sp d2 as shown in Fig. 6.lf. 

Sulfur, unlike oxygen, has the capacity to expand its valence shell beyond the normal octet of electrons to form hypervalent compounds such as sulfur tetrafluoride (SF4) with 10 electrons in the outermost shell and sulfur hexafluoride (SF6) containing 12 electrons in the valence shell.63,7 The chemistry of hypervalent sulfur started in 1873 with the discovery of the unstable compound sulfur tetrachloride (SCI4). The existence of hypervalent sulfur compounds is an important feature of the chemistry of sulfur and the precise nature of the bonding in these molecules has remained a puzzling problem. 

The heavier elements of the group, S, Se and Te all form tetralluorides, EF4 and hexafluorides, EF6- If the central atom in these compounds form Lewis electron pair bonds to all the ligating fluorine atoms, it must accommodate five or six electron pairs in the valence shell, and we refer to the atoms as hypervalent. Sulfur forms no further homoleptic hypervalent derivatives. Selenium forms a solid tetrachloride, but as mentioned in the last paragraph, it decomposes on evaporation. Tellurium forms a solid tetrachloride, which may be evaporated without decomposition, as well as tetraphenyl-, tetramethyl- and hexamethyl- derivatives. 

Another example of a central atom with an expanded valence shell is sulfur hexafluoride, SFg, a remarkably dense and inert gas used as an insulator in electrical equipment. The central sulfur is surrounded by six single bonds, one to each fluorine, for a total of 12 electrons ... 

All bonding groups octahedral shape (AXg). When seesaw-shaped SF4 (discussed above) reacts with more F2, the central S atom expands its valence shell further to form octahedral sulfur hexafluoride (SFg) ... 

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