Extranuclear particles

The six extranuclear electrons from the carbon plus the one corresponding to the beta particle are exactly the seven needed for the nitrogen atom. Thus, the energy may be calculated from the difference between the atomic masses ... 

It was perhaps Thomson who first suggested a specific structure for the atom in terms of subatomic particles. His plum pudding model (ca. 1900), which placed electrons in a sea of positive charge, like raisins in a pudding., accorded with the then-known facts in evidently permitting electrons to be removed under the influence of an electric potential. The modem picture of the atom as a positive nucleus with extranuclear electrons was proposed by Rutherford13 in 1911. It arose from... 

A multitude of concepts such as X-ray, neutron and electron diffraction, X-ray crystallography, low-angle scattering, powder diffraction, scattering by noncrystalline and amorphous solids, all refer to the same physical phenomenon. Whereas X-rays and electrons are scattered by extranuclear charge clouds, more massive particles like neutrons and a-particles are scattered on atomic nuclei. In principle, all of these processes are of the same type, as described for X-rays below. 

All the types of interatomic binding force to which we have referred above are primarily electronic in nature, and the differences between them arise from differences in the electronic structures of the particles concerned. In order that we may be able to understand the origin of these forces and to predict the types of force likely to operate in any particular structure it is therefore necessary that we should have a clear picture of the extranuclear electron distribution in the atoms of the elements, and of the way in which this distribution changes as we pass from one element to another in the Periodic Table. The rest of this chapter is accordingly devoted to a discussion of this topic and will serve as an introduction to the remaining four chapters of Part I, in which the different types of interatomic binding force are considered individually. 

In 1911, the British physicist and Nobel laureate Ernest Rutherford (1871-1937) published the article The Scattering of Alpha and Beta Particles by Matter and the Structure of the Atom in Philosophical Magazine. In this article, Rutherford reported the results of an experiment that demonstrated that the protons and electrons in atoms are not distributed homogeneously. Instead, the protons are concentrated in a relatively tiny region Rutherford called the nucleus (from the Latin, meaning kernel ). The electrons are extranuclear electrons are located in a relatively much larger volume of space surrounding the nucleus. Rutherford s discovery of the nucleus was immediately accepted within the scientific community. However, the relationship, if any, between atomic structure and properties was still unclear. 

The Harkins theory of nuclear structure was formulated before the discovery of the neutron, but predicted the existence of this particle. An atom was described in terms of a mass number, P, that specihes the number of protons in a nucleus, an atomic number Z, that specihes the number of extranuclear electrons and the number of nuclear electrons, N. Another fundamental quantity was dehned as the isotopic number... 

Electron i- lek- tran [electr- + -on] (1891) n. A (perhaps) fundamental subatomic particle with a very low mass and a unit negative electrical charge found in the extranuclear region of an atom. The electron is a small... 

Poly(ADP-ribosyl)ation is generally described as a nuclear event. However, extranuclear poly(ADP-ribose) polymerase activities have been detected in the cytosol of baby hamster kidney ceUs (1), the ribosomal fraction of HeLa cells (2) and rat testis (3). The activities looked like the nuclear enzyme in diat they totally or partially depended on DNA. We have previously reported the association of a poly(ADP-ribose) polymerase with a specific ribonucleoprotein complex, namely free messenger ribonucleoprotein particles (free mRNP) (4-6). The enzyme has the particularity to be DNA-independent. In diis paper, we have b n interested in the proteins which are poly(ADP-ribosyl)ated in free mRNP. We also present evidence of the existence of a poly(ADP-ribose) glycohydrolase in free mRNP. 

A principal aim of chemical analysis is to develop a theoretical model of the interaction between atoms and molecules. Experimental work of the previous two centuries has resulted in a highly successful empirical account of chemical reactivity, and efforts to formulate a rigorous, fundamental theory as a nonclassical many-body problem have lead to highly accepted and much used methods but these still have significant limitations. By the current approaches, chemical interaction is modeled in terms of probability-density distributions of independent electrons. Although the theory appears to work for one-particle problems, unforeseen effects emerge in the treatment of more complex systems [1]. In particular, the distribution of extranuclear electrons seems to obey an exclusion principle, not anticipated in the basic theory, and there is no fundamental understanding of three-dimensional molecular shapes, as observed experimentally. The pivotal role of entropy, which controls the course of chemical reactions, is theoretically equally unexpected. 

Deshpande, A., Goodwin, E.H., Bailey, S.M., et al., 1996. Alpha-particle-induced sister chromatid exchange in normal human lung fibroblasts evidence for an extranuclear target. Radiat. Res. 145 (3), 260-267. 

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