Characteristics of multiple N,O bonds.

The electron distribution for N,O bonds in a wide range of molecules is analyzed using Bader's atoms in molecules theory and measures of bond order. It is shown that electron density derived parameters correlate very well with bond length and bond orders. An unexpectedly large number of bond orders are near to or greater than 2, indicating that nitrogen is effectively pentavalent in a many simple molecules. This conclusion is substantiated by examination of the Laplacian of the electron density. Such hypervalence indicates that nitrogen does not always obey the classical octet rule.