SF6
Sulfur hexafluoride (4.5) provides an example of a so-called
hypervalent molecule, i.e. one in which the central atom
appears to expand its octet of valence electrons. However,
a valence bond picture of the bonding in SF6 involving
resonance structures such as 4.6 shows that the S atom
obeys the octet rule. A set of resonance structures is
needed to rationalize the observed equivalence of the six
SF bonds. Other examples of ‘hypervalent’ species of the
p-block elements are PF5, POCl3, AsF5 and [SeCl6]2. The