среда, 25 марта 2020 г.
Homework
1. Unit 5. Text "The periodic table of the chemical elements" on pages 31-32.(to translate);
Dmitri Mendeleev
Dmitri Mendeleev
Dmitri Mendeleev, Russian in full Dmitry Ivanovich Mendeleyev (1834-1907), Russian chemist who developed the periodic classification of the elements. Mendeleev found that, when all the known chemical elements were arranged in order of increasing atomic weight, the resulting table displayed a recurring pattern, or periodicity, of properties within groups of elements. In his version of the periodic table of 1871, he left gaps in places where he believed unknown elements would find their place. He even predicted the likely properties of three of the potential elements. The subsequent proof of many of his predictions within his lifetime brought fame to Mendeleev as the founder of the periodic law.
Mendeleev was born in the small Siberian town of Tobolsk . In1848 Dmitri enrolled in the Main Pedagogical Institute in St.Petersburg. Mendeleev graduated in 1855. He received a master’s degree in 1856 and began to conduct research in organic chemistry.
In 1861 Mendeleev returned to St. Petersburg, where he obtained a professorship at the Technological Institute in 1864. After the defense of his doctoral dissertation in 1865 he was appointed professor of chemical technology at the University of St. Petersburg (now St. Petersburg State University). He became professor of general chemistry in 1867 and continued to teach there until 1890.
As he began to teach inorganic chemistry, Mendeleev could not find a textbook that met his needs. Since he had already published a textbook on organic chemistry in 1861 that had been awarded the prestigious Demidov Prize, he set out to write another one. The result was Osnovy khimii (The Principles of Chemistry), which became a classic, running through many editions and many translations.
When Mendeleev began to compose the chapter on the halogen elements at the end of the first volume, he compared the properties of this group of elements to those of the group of alkali metals such as sodium. Within these two groups of dissimilar elements, he discovered similarities in the progression of atomic weights, and he wondered if other groups of elements exhibited similar properties. After studying the alkaline earths, Mendeleev established that the order of atomic weights could be used not only to arrange the elements within each group but also to arrange the groups themselves. Thus, in his effort to make sense of the extensive knowledge that already existed of the chemical and physical properties of the chemical elements and their compounds, Mendeleev discovered the periodic law.
His newly formulated law was announced before the Russian Chemical Society in March 1869 with the statement “elements arranged according to the value of their atomic weights present a clear periodicity of properties.” Mendeleev’s law allowed him to build up a systematic table of all the 70 elements then known. He had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and predicted the locations within the table of unknown elements together with their properties. At first the periodic system did not raise interest among chemists. However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.
Mendeleev was born in the small Siberian town of Tobolsk . In1848 Dmitri enrolled in the Main Pedagogical Institute in St.Petersburg. Mendeleev graduated in 1855. He received a master’s degree in 1856 and began to conduct research in organic chemistry.
In 1861 Mendeleev returned to St. Petersburg, where he obtained a professorship at the Technological Institute in 1864. After the defense of his doctoral dissertation in 1865 he was appointed professor of chemical technology at the University of St. Petersburg (now St. Petersburg State University). He became professor of general chemistry in 1867 and continued to teach there until 1890.
As he began to teach inorganic chemistry, Mendeleev could not find a textbook that met his needs. Since he had already published a textbook on organic chemistry in 1861 that had been awarded the prestigious Demidov Prize, he set out to write another one. The result was Osnovy khimii (The Principles of Chemistry), which became a classic, running through many editions and many translations.
When Mendeleev began to compose the chapter on the halogen elements at the end of the first volume, he compared the properties of this group of elements to those of the group of alkali metals such as sodium. Within these two groups of dissimilar elements, he discovered similarities in the progression of atomic weights, and he wondered if other groups of elements exhibited similar properties. After studying the alkaline earths, Mendeleev established that the order of atomic weights could be used not only to arrange the elements within each group but also to arrange the groups themselves. Thus, in his effort to make sense of the extensive knowledge that already existed of the chemical and physical properties of the chemical elements and their compounds, Mendeleev discovered the periodic law.
His newly formulated law was announced before the Russian Chemical Society in March 1869 with the statement “elements arranged according to the value of their atomic weights present a clear periodicity of properties.” Mendeleev’s law allowed him to build up a systematic table of all the 70 elements then known. He had such faith in the validity of the periodic law that he proposed changes to the generally accepted values for the atomic weight of a few elements and predicted the locations within the table of unknown elements together with their properties. At first the periodic system did not raise interest among chemists. However, with the discovery of the predicted elements, notably gallium in 1875, scandium in 1879, and germanium in 1886, it began to win wide acceptance. Gradually the periodic law and table became the framework for a great part of chemical theory. By the time Mendeleev died in 1907, he enjoyed international recognition and had received distinctions and awards from many countries.
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