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Scientists Contribution to the periodic table.
Transcript of Scientists Contribution to the periodic table.
Johann Wolfgang Döbereiner
Johann Wolfgang Döbereiner (13 December 1780 – 24 March 1849) was a German chemist who is best known for work that foreshadowed the periodic law for the chemical elements. In the 1800s, J.W.Dobereiner tried grouping elements into triads. In chemistry, a triad is a set of three elements with similar properties. Chlorine, bromine, and iodine formed one triad because they behave in similar ways. For example, they all react easily with metals. Triads worked for some elements, but not for all known elements. Dobereiner was not the only person to try to organize the elements. Before 1869, many systems were proposed but none were widely accepted.
Dmitri Ivanovich Mendeleev (8 February 1834 – 2 February 1907) was a Russian chemist and inventor. By the 1860s, more than 60 elements were known to the world. At that time, Dmitri Mendeleev, a Russian chemist, was working on a textbook. He wanted a way to show his students how all the known elements are related. He wrote the properties of each element on a separate note card. He moved the cards around until he fund an organization that worked. He hose a table in which the elements were arranged in order by atomic mass.
John Alexander Reina Newlands
John Alexander Reina Newlands (26 November 1837 – 29 July 1898) was an English chemist who worked on the development of the periodic table. Newlands was the first person to devise a periodic table of elements arranged in order of their relative atomic weights. Continuing Johann Wolfgang Döbereiner’s work with triads and Jean-Baptiste Dumas' families of similar elements, he published in 1865 his 'Law of octaves', which stated that "any given element will exhibit analogous behaviour to the eighth element following it in the table." Newlands’ arranged all of the known elements into seven groups, which he likened to the octaves of music.
A few elements, such as gold silver, have been known for thousands of years]. Yet only 13 element had been identified by the year 1700. Chemists expected to discover other elements. As they began to use scientific methods to search for elements, the rate of discovery increased. How would chemists know when they had discovered all the element? To begin answer the question, chemists needed to find a logical way to organize the elements.
By : Avisha Patel
Henry Gwyn Jeffreys Moseley (23 November 1887 - 10 August 1915) was an English Physicits. Moseley's law advanced atomic physics by providing the first experimental evidence in favour of Niels Bohr's theory, aside from the hydrogen atom spectrum which the Bohr theory was designed to reproduce. That theory refined Ernest Rutherford's and Antonius van den Broek's model, which proposed that the atom contains in its nucleus a number of positive nuclear charges that is equal to its (atomic) number in the periodic table. This remains the accepted model today.