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

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 PCl 5 and SF 6 , 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 wellknown gaseous molecules having one or several single-bonded elements. A future paper will discuss the application of the even-odd rule to charged molecules.

How the Even-Odd Rule, by Defining Electrons Pairs and Charge Positions, Can Be Used as a Substitute to the Langmuir-Octet Rule in Understanding Interconnections between Atoms in Ions and Molecules

“…This discussion is more general than in previous paper, which was focused on the validity of the rules [6]- [8].…”

“…An important key to the validity of the even-odd rule is that the number of electrons in every shell is an even number. Specifically for the inactive shell, the even number of electrons imposes that molecules and ions belong to a group of electron-paired compounds [6] [7] i.e. molecules at standard energy scale [5].…”

“…In previous papers, the even-odd drawing procedure has been applied to every atom of many ions or molecules [6]- [8]. In this chapter, the rule is applied to atoms in 3D molecules: two examples are displayed in Table 2 and Table 3.…”

Difference in Number of Electrons in Inner Shells of Charged or Uncharged Elements in Organic and Inorganic Chemistry: Compatibility with the Even-Odd Rule

“…In an attempt to have a unified rule applicable to a wider number of molecules, a new rule named the even-odd rule was recently proposed [8]. Following articles have investigated additional ions and molecules and confirmed the applicability of the even-odd rule to a great number of compounds [9] [10] [11].…”

“…On notation and terminology, the reader should also take good notice that ions or molecules bearing an overall charge will be written after these examples: H2O for neutral water, H3O(+) for positive water ions and OH(−) for negative water ions [8] [9] [10] [11].…”