8. перепишите и переведите текст контрольной работы № 3. задайте 5 общих и 5 специальных вопросов к тексту. d.i. mendeleyev – pride of russian science d.i. mendeleyev was born in tobolsk in 1834. in 1850 at the age of 16 he entered the pedagogical institute in st. petersburg to study chemistry. five years later he graduated from it with a gold medal and was invited to lecture on theoretical and organic chemistry at st. petersburg university. to continue his studies and research mendeleev was sent to germany in 1859. while living abroad he made a number of important investigations. the year 1868 was the beginning of his highly important work “fundamentals of chemistry”. working at this subjects mendeleev analysed an enormous amount of literature, made many experiments and calculations. this tremendous work resulted in the table of elements consisting of vertical groups and horizontal periods. he was the first to suggest a system of classification in which the elements are arranged in the in the order of increasing atomic weights. the main idea of the periodic system is the idea of periodic repetition of properties with the increase of the atomic weights. arranging all the existing elements in the table mendeleev had to overcome great difficulties, as a considerable number of elements were unknown at that time and the atomic weights of 9 elements (out of 63) were wrongly determined. thanks to his investigations mendeleev was able to predict not only the existance of a few unknown elements but their properties as well. he died in 1907 at the age of 73.

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