Paul, Jones, and Karl
Dmitri Ivanovich Mendeleev was born in Tobol'sk, Siberia on February 7, 1834. Mendeleev was born into a family in which he was the youngest of 17 children. His father was the head of the local high school, but went blind when Mendeleev was just a child. Mendeleev's mother was then left to raise her children. Mendeleev was educated locally, but couldn't get into any university until 1855 when he finally qualified as a teacher at the Pedagogical Institute in St. Petersburg. There he took an advanced degree course in chemistry, and in 1857 received his first university job. In 1861 Mendeleev returned to St. Petersburg and became Professor of General Chemistry at the Technical Institute there in 1864. He couldn't find a sufficient textbook for students, so he wrote his own- "Principles of Chemistry".
In the late 1860's, Mendeleev began his work on the periodic law. Mendeleev's first version of the periodic table had 57 elements. Mendeleev was convinced that the order of the elements lay in their atomic weights, and so this is how he arranged his periodic table: in sequence of increasing atomic weights. When Mendeleev did this, he noted that the chemical properties of the elements were grouped into already familiar families. He did not have any theory to explain his table. The second part of the arrangement of Mendeleev's periodic table lay in the similarities of the elements when the table was read from top to bottom. When he reached an element with properties similar to the first one in the first row, a new row was started. Out of all of the elements Mendeleev organized into his table, the only one he coulnd't fit into his pattern was hydrogen. He simply placed this element in a box on its own. However, there were some elements that would not fit properly using the then atomic weights, so he altered the atomic weights of some of the elements (changed indium from 76 to 114 and beryllium from 13.8 to 9.2). Although Mendeleev had a good number of elements included in his table, he knew that he didn't have them all, because they simply hadn't all been discovered. He did, however, have a plan for those elements too.
It did not take long for Mendeleev to discover that he had to leave spaces in his table for future elements, because he knew that they hadn't all been discovered. He was also able to predict the properties of the elements that should occupy the spaces. This greatly helped scientists in knowing where to look to discover new elements. Because of Mendeleev, they knew properties of elements they hadn't even discovered. Mendeleev's predictions proved true when the elements gallium, scandium, and germanium were discovered and their properties fit perfectly into the blank spaces Mendeleev had provided. At this point, his periodic table was accepted, and it quickly became one of the true cornerstones of chemistry. Inert gases xenon and krypton, and the radioactive elements were found mainly through using Mendeleev's periodic table. These are only some of the examples of elements that were found using his periodic table.
Probably the biggest change that has been made to Dmitri Mendeleev's periodic table is today, the periodic table is organized by atomic number, as opposed to atomic weight, which is how Mendeleev's was organized. Atomic number is based on the number of neutrons, while atomic weight is the sum of the numbers of protons and neutrons in the nucleus. This revision to Mendeleev's periodic table has been made because the atomic number is a better indicator of an element's properties than its atomic weight. Besides this, most of the changes that have been made to the periodic table are really just additions; additions of elements that had yet to be discovered when Mendeleev constructed his periodic table.
Dmitri Mendeleev, five days prior to his seventy-third birthday, died in St. Petersburg on February 2, 1907. Just one year before, Mendeleev was nominated for the 1906 Nobel Prize for Chemistry. He lost the race to Henri Moissan by just one vote, but Mendeleev was honored 50 years later when the 101st element was named after him: mendelevium. Overall, Dmitri Ivanovich Mendeleev had a huge impact on the world. During a time in which technology was much more primitive, this amazingly knowledgeable chemist was able to construct a periodic table that is very similar to the one we use today. Without Mendeleev, the world of chemistry would most likely be a lot less complete.
"Dmitryi Ivanovitch Mendeleev (1834-1907)." Zephyrus. 1 Oct. 2006 <http://zephyrus.co.uk/
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