TITLE:
Improvement of the Lewis-Abegg-Octet Rule Using an “Even-Odd” Rule in Chemical Structural Formulas: Application to Hypo and Hyper-Valences of Stable Uncharged Gaseous Single-Bonded Molecules with Main Group Elements
AUTHORS:
Geoffroy Auvert
KEYWORDS:
Octet Rule, Hypervalence, Hypovalence, Even-Odd, Rule, Electron-Pair, Single Bond, Molecule, Chemistry
JOURNAL NAME:
Open Journal of Physical Chemistry,
Vol.4 No.2,
May
23,
2014
ABSTRACT: As Lewis proposed
his octet rule, itself inspired by Abegg’s rule, that a molecule is stable when
all its composing atoms have eight electrons in their valence shell, it
perfectly applied to the vast majority of known stable molecules. Only a few
stable molecules were known that didn’t fall under this rule, such as PCl5 and SF6, and Lewis chose to leave them aside at the time of his
research. With further advances in chemistry, more exceptions to this rule of
eight have been found, usually with the central atom of the structure having
more or less than eight electrons in its valence shell. Theories have been
developed in order to modify the octet rule to suit these molecules, defining
these as hyper- or hypo-valent molecules and using other configurations for the
electrons. The present paper aims to propose a representation rule for gaseous
single-bonded molecules that makes it possible to reconcile both; molecules
following the octet theory and those which do not. In this representation rule,
each element of the molecule is subscripted with two numbers that follow a set
of simple criteria. The first represents the number of valence electrons of the
element; while the second is calculated by adding the first number to the
number of the element’s covalent bonds within the molecule. The latter is equal
to eight for organic molecules following the octet rule. Molecules being
exceptions to the octet rule are now encompassed by this new even-odd rule:
they have a valid chemical structural formula in which the second number is
even but not always equal to eight. Both rules—octet and even-odd—are discussed and
compared, using several well-known gaseous molecules having one or several
single-bonded elements. A future paper will discuss the application of the
even-odd rule to charged molecules.