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Hennig Brand
The elements like gold, silver, copper, Tin, Lead and mercury have been known since antiquity. The first scientific discovery was in 1649 when Hennig Brand discovered the element phosphorous. -
Henry Cavendish
Henry Cavendish discoveres hydrogen. He discribes it as a colorless, odourless gas that burns and can form an explosive mixture with air. -
John Dalton
John Dalton proposes "Dalton's Law" which describes the relationship between the different components in a mixture of gases. This discovery helps future scientists isolate a mixture of gases for individual study. -
Johann Dobereiner
In 1817 Johann Dobereiner noticed that the atomic weight of strontium fell midway between the weights of calcium and barium, elements possessing similar chemical properties. In 1829, after discovering the halogen triad composed of chlorine, bromine, and iodine and the alkali metal triad of lithium, sodium and potassium he proposed that nature contained triads of elements the middle element had properties that were an average of the other two members when ordered by the atomic weight. -
A.E.Beguyer de Chancourtois
the first person to make use of atomic weights to reveal that the elements were arranged according to their atomic weights with similar elements occurring at regular intervals -
John Newlands,
He wrote a paper which classified 56 elements into 11 groups based on similar physical propertiees. 1864 he pulished his version of the periodic table -
Dmitri Ivanovich Mendeleev
Mendeleev noticed patterns in the properties and atomic weights of halogens, alkali metals and alkaline metals. In an effort to extend this pattern to other elements, he created a card for each of the 63 known elements. Each card contained the element's symbol, atomic weight and its characteristic chemical and physical properties. When Mendeleev arranged the cards on a table in order of ascending atomic weight grouping he formed the period table. -
Henry Moseley
Henry Moseley determined the atomic number of each of the known elements. he noticed that if the elements were ordered in the order of increasing atomic number rather than atomic weight, they gave a better fit within the ‘periodic table’
