The Concept Of Electronegativity

Pritchard, H. O.; Skinner, H. A.

doi:10.1021/cr50004a005

Cited by 602 publications

(181 citation statements)

References 48 publications

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“…Ever since the beginning of the electronegativity concept, the importance of the chemical environment to the electronegativity has been stressed repeatedly. 177,184,186,210,211 Huheey summed up this sentiment most directly in the following way "Electronegativity is not a property of the isolated atom but rather a property of an atom in a molecule, in the environment of and under the influence of surrounding atoms." 212 While that much everybody agrees on, the problem, as it always has been, is how to define a "molecular" environment for an atom without actually putting it in a molecule.…”

Section: Charge Transfer In Moleculesmentioning

confidence: 99%

The physics and chemistry of the Schottky barrier height

Tung

2014

Applied Physics Reviews

1,072

479

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The formation of the Schottky barrier height (SBH) is a complex problem because of the dependence of the SBH on the atomic structure of the metal-semiconductor (MS) interface. Existing models of the SBH are too simple to realistically treat the chemistry exhibited at MS interfaces. This article points out, through examination of available experimental and theoretical results, that a comprehensive, quantum-mechanics-based picture of SBH formation can already be constructed, although no simple equations can emerge, which are applicable for all MS interfaces. Important concepts and principles in physics and chemistry that govern the formation of the SBH are described in detail, from which the experimental and theoretical results for individual MS interfaces can be understood. Strategies used and results obtained from recent investigations to systematically modify the SBH are also examined from the perspective of the physical and chemical principles of the MS interface.

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Section: Charge Transfer In Moleculesmentioning

confidence: 99%

The physics and chemistry of the Schottky barrier height

Tung

2014

Applied Physics Reviews

1,072

479

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“…Interested readers are directed to relevant reviews [221][222][223][224]. In addition, a lucid treatment by Huheey [225] and two recent publications [226,227] provide good summaries of and references to the various approaches, while two commentaries on EN scales by Pearson [228] and Allen [229], albeit now somewhat dated, give some of the flavor of past debates on the subject.…”

Section: Appendix B: Electronegativity (En)mentioning

confidence: 99%

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Karen

McArdle

Takats

2014

Pure and Applied Chemistry

111

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A generic definition of oxidation state (OS) is formulated: "The OS of a bonded atom equals its charge after ionic approximation". In the ionic approximation, the atom that contributes more to the bonding molecular orbital (MO) becomes negative. This sign can also be estimated by comparing Allen electronegativities of the two bonded atoms, but this simplification carries an exception when the more electronegative atom is bonded as a Lewis acid. Two principal algorithms are outlined for OS determination of an atom in a compound; one based on composition, the other on topology. Both provide the same generic OS because both the ionic approximation and structural formula obey rules of stable electron configurations. A sufficiently simple empirical formula yields OS via the algorithm of direct ionic approximation (DIA) by these rules. The topological algorithm works on a Lewis formula (for a molecule) or a bond graph (for an extended solid) and has two variants. One assigns bonding electrons to more electronegative bond partners, the other sums an atom's formal charge with bond orders (or bond valences) of sign defined by the ionic approximation of each particular bond at the atom. A glossary of terms and auxiliary rules needed for determination of OS are provided, illustrated with examples, and the origins of ambiguous OS values are pointed out. An electrochemical OS is suggested with a nominal value equal to the average OS for atoms of the same element in a moiety that is charged or otherwise electrochemically relevant.

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“…Since the biomolecules consist of the atoms C, N, O, P, let us find the plausible values of the Hückel parameters for them. The Pauling's electronegativity 105 for carbon (C), nitrogen (N), oxygen (O) and phosphorus (P) are given as follows:…”

Section: The Hückel Parameters For Biomoleculesmentioning

confidence: 99%

Π-Electrons IN a SINGLE STRAND OF DNA: A PHENOMENOLOGICAL APPROACH

Iguchi¹

2004

Int. J. Mod. Phys. B

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We revisit the problem of the electronic properties of a single strand of DNA, formulating the Hückel approximation for π-electrons in both the sugar-phosphate backbone chain and the π-stacking of nitrogenous bases in a single strand of DNA where the nitrogenous bases are adenine (A), guanine (G), cytosine (C) and thymine (T), respectively. We calculate the electronic band structure of π-electrons: (i) in the single nitrogenous base molecules such as A, G, C and T, (ii) in the single sugar-phosphate molecule, (iii) in the single nucleotide systems such as A, G, C, T with the single sugar-phosphate group, and (iv) in the system of a single strand of DNA with an infinite repetition of a nucleotide such as A, G, C and T, respectively. We find the following: In the case of (i), there is an energy gap between the energy levels for the HOMO and LUMO in the nitrogenous base. This guarantees the semiconducting character of the bases as a mother material. In the case of (ii), there are the HOMO localized at the oxygen site with a double bond and the LUMO localized around the phosphorus atom, which have a quite large energy gap. In the case of (iii), the energy levels for the HOMO and LUMO of the nitrogenous base remain almost the same as those of the nucleotide, while those of the sugar-phosphate group remain the same as well. The HOMO of the sugar-phosphate group exists right below the HOMO of the nitrogenous base. Therefore, comparing the energy levels for the HOMOs of the nitrogenous base group with those of the sugar-phosphate group, the nitrogenous base group behaves as a donor while the sugar-phosphate group behaves as an acceptor. In the case of (iv), there are energy bands and band gaps for the extended states in the nitrogenous base group and the sugar-phosphate group as well as the discrete levels for the localized states at the phosphate site in the spectrum. There is a transition from semiconductor to semimetal as the π-electron hopping between the nitrogenous bases of nucleotide is increased. The details of the above will be discussed in the present paper. Thus, we show the powerfulness of the Hückel theory in the study of DNA as well, although this theory is, at the first glance, oversimplified and purely phenomenological.

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The Concept Of Electronegativity

Cited by 602 publications

References 48 publications

The physics and chemistry of the Schottky barrier height

The physics and chemistry of the Schottky barrier height

Toward a comprehensive definition of oxidation state (IUPAC Technical Report)

Π-Electrons IN a SINGLE STRAND OF DNA: A PHENOMENOLOGICAL APPROACH

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