Читать книгу Foundations of Chemistry - Philippa B. Cranwell - Страница 104

When there are six areas of electron density around the central atom or six single covalent bonds, the molecule adopts an octahedral shape. If all six bonded atoms are identical, the angle between each of the bonds is 90°, as this is the furthest apart that all six components can arrange themselves around the central atom. Figure 2.18 depicts the shape of the sulfur hexafluoride, SF₆ molecule: the six fluorine atoms arrange themselves as far apart as possible around the central sulfur atom. The reason for the name octahedral is that the shape made by the six bonds from a central atom has eight faces, which is an octahedron.

SF₆ is used extensively in insulating high‐voltage electrical transmittance cables and switching gear. It is now known to be the most potent greenhouse gas and is banned in all applications apart from in the electrical industry.

Figure 2.18 (a) Bonding angles in an octahedral molecule; (b) sulfur hexafluoride, SF₆ superimposed into an octahedron.