Atomic Number - Research Article from World of Earth Science

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Atomic Number

Atomic number is defined as the number of protons in the nucleus of an atom. This concept was historically important because it provided a theoretical basis for the periodic law. Dmitri Mendeleev's discovery of the periodic law in the late 1860s was a remarkable accomplishment. It provided a keyorganizing concept for the chemical sciences. One problem that remained in Mendeleev's final analysis was the inversion of certain elements in his periodic table. In three places, elements arranged according to their chemical properties, as dictated by Mendeleev's law, are out of sequence according to their atomic weights.

The solution to this problem did not appear for nearly half a century. Then, it evolved out of research with x rays, discovered in 1895 by Wilhelm Röntgen. Roentgen's discovery of this new form of electromagnetic radiation had inspired a...

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This section contains 514 words
(approx. 2 pages at 300 words per page)
Buy the Atomic Number Encyclopedia Article
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Gale
Atomic Number from Gale. ©2005-2006 Thomson Gale, a part of the Thomson Corporation. All rights reserved.
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