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Orbitals and Bonding
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
The octet rule states that every atom wants to have eight valence electrons in its outermost electron shell. What is valence?
Organic Chemistry Nomenclature
Published in Arthur W. Hounslow, Water Quality Data, 2018
The Octet rule states that an atom tends to gain or lose electrons until there are eight electrons in its outer shell, thus attaining a stable, inert gas configuration. Exceptions to this rule include some of the transition elements. Ionic solids are dissociated (separated) by water dipoles.
Introduction to Organometallics
Published in Samir H. Chikkali, Metal-Catalyzed Polymerization, 2017
Samir H. Chikkali, Sandeep Netalkar
Before we start with 18-electron rule, let us first recall the Octet rule. The Octet rule states that atoms such as carbon with one 2s and three 2p orbitals require eight electrons to completely fill the valence shell and compounds, which can fulfill this requirement are left with no or little tendency to participate in chemical reactions, thus achieve stability. There is a similar tendency with metals to react with ligands forming organometallic or coordination complexes in such a way as to attain the electronic configuration of next inert gas in the series [ns2(n−1)d10np6]. The 18-electron rule states that a metal complex with 18 electrons (filled valance shell or completes the insert gas configuration) in its outer shell will be stable as compared to the metal complexes either less than or more than 18 electrons. This is just a rule of thumb and there can be many exceptions to this rule; nevertheless, it offers guidelines to the chemistry of coordination and organometallic compounds. For example, if there is a competition of any given metal with two sets of ligands, one which yields the complex 18-electron configuration and the other less or more than 18-electron configuration, then the metal will prefer the former ligand over later due to the obvious reason of stability. The valence electron count of a complex includes the valence electrons of the central metal ion and the electrons shared or donated by the ligands, and for inert gas configuration it comes to 18. Counting the valence electrons in a complex allows us to predict the stability associated with complex and also to predict the mechanism and mode of reactivity to achieve 18-electron configuration.
Unwise Relationships and an Unsound Valence Theory: The Chemical Career of Robert Fergus Hunter (1904–1963)
Published in Ambix, 2021
William H. Brock, Michael Jewess
The key observations on which this pre-quantum-mechanical strand of theory (1) was based were these. First, most compounds were known to contain an even number of electrons and to be diamagnetic, suggesting that electron pairs were particularly stable. Secondly, at least the elements of groups 1–2 and 15–17 of the periodic table (modern numbering) strongly tended to form compounds in which their electron configuration, by ionisation or sharing of electron pairs, matched the electronic structure of the nearest “inert gas” (in modern terminology, the nearest “noble gas” of group 18). With the exception of He, which has just two electrons, the inert gas elements Ne to Rn have an outer electron shell of 8 electrons (on modern understanding an outer s2p6 configuration), so this was known as the “octet rule.”