TITLE:
The Even-Odd Rule on Single Covalent-Bonded Structural Formulas as a Modification of Classical Structural Formulas of Multiple-Bonded Ions and Molecules
AUTHORS:
Geoffroy Auvert
KEYWORDS:
Multiple Bond, Single Bond, Covalent Bond, Molecule, Ion, Even-Odd, Rule, Structural Formula
JOURNAL NAME:
Open Journal of Physical Chemistry,
Vol.4 No.4,
November
20,
2014
ABSTRACT: In organic chemistry, as defined by Abegg, Kossel, Lewis and
Langmuir, compounds are normally represented using structural formulas called
Lewis structures. In these structures, the octet rule is used to define the
number of covalent bonds that each atom forms with its neighbors and multiple
bonds are frequent. Lewis’ octet rule has unfortunately shown
limitations very early when applied to non-organic compounds: most of them
remain incompatible with the “rule of eight” and location of charges is
uncertain. In an attempt to unify structural formulas of octet and non-octet
molecules or single-charge ions, an even-odd rule was recently proposed,
together with a procedure to locate charge precisely. This even-odd rule has
introduced a charge-dependent effective-valence number calculated for each
atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These
numbers are both used to understand and draw structuralformulas of
single-covalent-bonded compounds. In the present paper, a procedure is proposed
to adjust structural formulas of compounds that are commonly represented with
multiple bonds. In order to keep them compatible with the even-odd rule, they
will be represented using only single covalent bonds. The procedure will then
describe the consequences of bond simplification on charges locations. The
newly obtained representations are compared to their conventional structural
formulas, i.e. single-bond representation vs.
multiple-bond structures. Throughout the comparison process, charges are
precisely located and assigned to specific atoms. After discussion of
particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.