Методическая разработка по английскому языку для студентов факультета химии и химической технологии " Simple Chemistry" Алматы 2017
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мет. разработка по химии
| Periodic table and Periodic law
The periodic table is a tabular display of the chemical elements, which is arranged based on their atomic numbers and chemical properties. Elements are presented by the increase of atomic number. The main body of the table is a 18 × 7 grid, and elements with the same number of valence electrons are kept together in groups, such as the halogens and the noble gases. The Periodic table can help predict the properties of various elements and the relations between properties. As a result, it provides a useful framework for the analyses of chemical behavior, and is widely used in chemistry and other sciences. The Periodic table was created by Dmitri Mendeleev in 1869. All elements from atomic numbers 1 (hydrogen) to 118 (ununoctium) have been synthesized. Of these, all up to and including californium exists naturally; the rest have only been artificially synthesized in laboratories, along with numerous synthetic radionuclides of naturally occurring elements. One of the cornerstones of modern chemical theory is the Periodic Law. It can be simply stated as follows: The properties of the elements are a periodic function of the nuclear charges of their atoms. In 1869 Mendeleyev arrived at the conclusion that by the arrangement of the elements in order of the increase of atomic weight the similarity and periodicity of properties of various, valence groups of the elements were clearly delineated. There were several vacant spaces in Mendeleyev's table which led him to predict the existence of six undiscovered elements, (scandium, gallium, germanium, polonium etc). His confidence in the new classification was clearly expressed in the predictions which he made of the chemical properties of these missing elements. And within fifteen years gallium, scandium and germanium were discovered. Although this table has been modified hundreds of times, it has withstood the onslaught of all new facts. Isotopes, rare gases, atomic numbers, and electron configurations have only strengthened the idea of the periodicity of the properties of the elements. жүктеу/скачать 422,31 Kb. Достарыңызбен бөлісу:
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