Chemistry

The Formation and Expansion of the Periodic Table of the Elements



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The periodic table is an organized table displaying chemical elements by their increasing atomic number. The table subdivides elements by their unique properties. The modern periodic table has expanded from the time the table’s creator Dmitri Mendeleev developed it to include the first known 63 elements. It has grown to include more than 117 elements. Though other system of characterizations existed before the periodic table, Mendeleev’s has become the standard for scientists.

Early Systems of Categorizing Elements

Frenchman Antoine Lavoisier was one of the earliest people to create a system of categorizing chemical elements. Commonly called the Father of Modern Chemistry, Lavoisier conducted experiments that showed the difference between different elements and he studied combustion and respiration. In 1787, he and a group of scientists created the Method of Chemical Nomenclature to classify elements and compounds. A few years later, in 1789, he published “An Elementary Treatise on Chemistry,” considered the first chemistry textbook. The publication listed 33 elements.

In the 19th century, scientists around the world who studied the elements began examining their chemical properties, atomic weights and chemical reactions. A contemporary and competitor of Mendeleev, German chemist Julius Lothar Meyer arranged 28 elements into six families based on chemical and physical characteristics on a table. He published his findings in the 1864 edition of Die modernen Theorien der Chemie. He left blanks in his table for undiscovered elements.

Mendeleev’s Work

While other scientists continued identifying and classifying elements, Mendeleev’s name would prove to be the one used for the periodic table as it is known today. His table proved similar to that constructed by Meyer. He listed the elements in rows and columns according to their atomic weight. Like other scientists, Mendeleev left gaps in his table for undiscovered elements. His book “The Principles of Chemistry displayed the table he created for the then known elements. He predicted the discovery of new elements, which drew skeptics. New elements, though, were discovered before his death in 1907.

New Developments in the 20th Century and Beyond

Scientists continued filling the gaps in the periodic table created by Mendeleev, as they continued making discoveries of naturally occurring elements. Something extraordinary occurred in 1940 when plutonium was produced synthetically. Nuclear chemist Glenn T. Seaborg and his colleagues at UC-Berkeley identified plutonium in 1941 but waited until after World War II in 1948 to reveal this scientific discovery. The United States Environmental Protection Agency says it is formed from uranium in nuclear reactors. Traces of plutonium occur naturally in uranium ore and other elements, such as californium. In 2012, elements flerovium and livermorium were discovered.

Conclusion

Although Mendeleev is given credit for creating the periodic table of the elements, scientists before him tried characterizing elements found in nature. Mendeleev, though, set the standard for subsequent scientists who discovered elements to fill in the blanks in his chart. As time progresses, the periodic table will likely continue expanding to include new elements.


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