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Johann Dobereiner put forward his law of triads in 1817
Each of Dobereiner's triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other.Atomic masses At this time, scientists had begun to find out the relative atomic masses of the elements. Dobereiner discovered that the relative atomic mass of the middle element in each triad was close to the average of the relative atomic masses of the other two elements. -
John Newlands put forward his law of octaves in 1864
He arranged all the elements known at the time into a table in order of relative atomic mass. When he did this, he found that each element was similar to the element eight places further on. For example, starting at Li, Be is the second element, B is the third and Na is the eighth element.Regular repeats Newlands' table showed a repeating or periodic pattern of properties, but it had problems. For example, he put iron in the same group as oxygen and sulphur, which are two non-metals. -
Dmitri Mendeleev
Mendeleev is best known for his work on the periodic table; arranging the 63 known elements into a Periodic Table based on atomic mass, which he published in Principles of Chemistry in 1869. His first Periodic Table was compiled on the basis of arranging the elements in ascending order of atomic weight and grouping them by similarity of properties. He predicted the existence and properties of new elements and pointed out accepted atomic weights that were in error. -
Meyer, Julius Lothar
lothar meyer devised a classification of elements into a table that accounted for the periodic variation in properties. his table included 56 elements.
This was earlier than Mendeleev's table (1869) but unfortunately Meyer's was not published until 1870. -
Lord Rayleigh
Lord Rayleigh helped with the discovery of the periodic table. Along with William Ramsey, they both discovered the inert gases on the periodic table. -
William Ramsay
Ramsay studied for an Arts degree at Glasgow University. After working in laboratories both there and on the Continent, he became Professor of Chemistry at the new Bristol University for seven years before joining UCL in 1887. Ramsay's most important contribution to science was the discovery of argon and the other noble gases for which he received the Nobel Prize in 1904. -
Henry Moseley
Henry Moseley is known for his establishment of truly scientific basis of the Periodic Table of the Elements by sorting chemical elements in the order of their atomic numbers. In his short career, he contributed a lot towards the science of physics through his research. -
Glenn T. Seaborg
"In 1944, Seaborg formulated the 'actinide concept' of heavy element electronic structure which predicted that the actinides – including the first eleven transuranium elements – would form a transition series analogous to the rare earth series of lanthanide elements. Called one of the most significant changes in the periodic table since Mendeleev's 19th century design, the actinide concept showed how the transuranium elements fit into the periodic table."
