Valence bond

A molecule containing certain atoms located in the space.One part of the molecule position can be determined which of course is the nucleus (Anpat alisis obtained through X-ray diffraction by crystals), whereas the can not be determined is the electron bonds that position change then followed addition of one electron to the atom. This section should not be ignored as a result of these changes is a contributing structure (or canonical structure) which is considered as a contributor in terms that can be measured as energy of the real structure. This molecule is known as a hybrid resonance from various contributors structures which differ only in terms of electron distribution valence, and expressed with a double arrow (↔). Although explained in terms of molecular energy it needs more contributors to the structure, but are often found single valence bond structure that is made is enough to be used to explain data qualitative molecules. For example, methane can be expressed as a structure of 1a and contribution in explaining the reaction mechanism omitted from the structure of 1b. In others, in explaining the polarity chloromethane, structure 2a is not sufficient to need donations of structure 2b.

System-π interactions between neighbors are often expressed resonance. Resonance require two or more valence bond structure in describing a molecule.

 Donations blind structure 3b and 3c-1 ,3-diene explain more in short and character of the double bond C2-C3 bond, while the number of contributors to the structure involved in describing the valence bond structure of benzene compounds (4) is a picture of symmetry properties of multiple-sixth of which this is not visible when just described with one single structure.

The weakness of this system in describing the qualitative structure is less compact molecular structures of these. Consequently, whenever necessary emphasis on certain traits of writing is required bond structure single valence main structure is a combination of a number of compounds in question.