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The history and chem. are described of onium compds., saltlike compds. contg. a complex cation in which the central atom is of an element with nonmetallic character. [on SciFinder (R)]
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A metalloid is a type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. There is no standard definition of a metalloid and no complete agreement on which elements are metalloids. Despite the lack of specificity, the term remains in use in the literature of chemistry. The six commonly recognised metalloids are boron, silicon, germanium, arsenic, antimony and tellurium. Five elements are less frequently so classified: carbon, aluminium, selenium, polonium and astatine.
History (derived ) is the systematic study and documentation of the human past. The period of events before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well as the memory, discovery, collection, organization, presentation, and interpretation of these events. Historians seek knowledge of the past using historical sources such as written documents, oral accounts, art and material artifacts, and ecological markers.
In chemistry, periodic trends are specific patterns that are present in the Periodic table that illustrate different aspects of certain elements when grouped by period and/or group. They were discovered by the Russian chemist Dmitri Mendeleev in the year 1863. Major periodic trends include atomic radius, ionization energy, electron affinity, electronegativity, valency and metallic character. These trends exist because of the similar electron configurations of the elements within their respective groups or periods; they reflect the periodic nature of the elements.
The article deals with different theories of history in the Soviet Union after 1945 and 1956, including quantitative problems, with reference to the heritage of the first half of the twentieth century. ...
This article focuses on the history of one specific area of the city of Tirana, the capital of Albania: the downtown area, or the so-called 'small ring'. The text analyzes the interventions put forward by different administrations (both right and left-wing ...
The subject of the article is the history of popular and authoritative series of St. Petersburg publishing house “Obrazovanie” (1909-1928), which on the eve of the First World War played an important role in Russia in the restructuring of key disciplines o ...
