Dmitri Ivanovich Mendeleyev
1834-1907
Russian Chemist
Dmitri Mendeleyev is best known for his development of the periodic table of the elements. His table is based on the patterns he observed when the elements are organized by increasing atomic weight. Using his table, he was able to accurately predict properties of previously unknown elements.
Mendeleyev was born in 1834 in Tobolsk, Russia. His father was a teacher who died by the time Dmitri was a teenager, and his mother opened a glass factory in order to support the large family. When Dmitri was old enough for college, his mother traveled with him across Russia to St. Petersburg, a journey of thousands of kilometers that they took largely on foot. There, in 1850, he enrolled in the Institute of Pedagogy to be educated as a teacher.
After graduating Mendeleyev continued his education at the University of St. Petersburg. He received an advanced degree in chemistry and was awarded a scholarship that allowed him to study in Europe. In 1860 he attended the Karlsruhe Conference in Germany. This conference was the first international meeting of chemists. One of the scientists Mendeleyev met there was Stanislao Cannizzaro (1826-1910), who had made accurate measurements of the atomic weights of the elements. These measurements were to be useful to Mendeleyev in his own research.
After returning to St. Petersburg Mendeleyev became a chemistry professor. He could find no textbook that was suited to his students' needs, so he decided to write his own. While working on his book, Principles of Chemistry (1868-1870), he began to look for a logical way of arranging the elements. He wrote the name of each element on a note card and listed its properties underneath. Then he began to arrange the cards in different ways, looking for patterns.
Eventually, Mendeleyev found that when he ordered the cards by increasing atomic weight, elements with similar properties appeared at regular, or periodic, intervals. Mendeleyev used his observations to make a table that reflected this pattern. This type of arrangement became known as a periodic table. (Mendeleyev's table forms the basis of the modern periodic table. However, the modern table is organized by increasing number of protons—atomic number—rather than increasing atomic weight.)
In March 1869 Mendeleyev presented his table to the Russian Chemical Society. Two years later, he published a revised and more detailed version. In the papers that accompanied these tables, Mendeleyev attempted to show that anelement's physical and chemical properties were a function of its atomic weight. Mendeleyev called this relationship the periodic law.
As he was working on his table, Mendeleyev began to suspect that there were elements that had yet to be discovered. (In fact, at that time scientists had described only 69 of the 112 chemical elements known today.) He left blanks in his table to accommodate these elements and even made predictions of their properties based on his periodic law. Three of these—gallium, scandium, and germanium—were discovered within 20 years of the publication of Mendeleyev's first table. When the scientific community realized that his predictions were accurate, Mendeleyev soon became quite well known and was frequently invited to give lectures throughout Europe.
Mendeleyev was not as accepted in Russia, however. He was considered controversial because he allowed women to attend his lectures and because he openly expressed his criticism of the Russian government. Although he was denied admission to the Russian Academy of Sciences, he was made director of the Bureau of Weights and Measures in 1893. Throughout his life he continued to write about chemistry as well as other topics, including education and art. In 1906 Mendeleyev missed being awarded the Nobel Prize in chemistry by a single vote.
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