Periodic Table History

HISTORY OF THE PERIODIC TABLE

Johann Döbereiner (1789-1849) was a German scientist who began to sort them and group them into triads (3 items), in which the atomic weight of the central elementwas almost the average of the other two. In 1829 Döbereiner, executed the first attempt for establishing a distribution in the elements, noticing on his projects the similarities between elements likechlorine, bromine and iodine in one side and the regular variation of their properties for other side. 
John Newlands 1864 The known elements were arranged in order of atomic weights and observedsimilarities between the first and ninth elements, the second and tenth elements etc. He proposed the 'Law of Octaves'. Newlands' Law of Octaves identified many similarities amongst the elements, but alsorequired similarities where none existed. He did not leave spaces for elements as yet undiscovered. 
Lothar Meyer 1869 Compiled a Periodic Table of 56 elements based on the periodicity of propertiessuch as molar volume when arranged in order of atomic weight. Meyer and Mendeleyev produced their Periodic Tables simultaneously. 
When Meyer was studying the atomic volume of the elements andrepresenting them face up the atomic mass, he observed the appearance on the graphic some waves. Each descent and increase represented for Meyer a period, name that is known until today, it showed that theproperties of the elements vary periodically according to their atomic number. Using a valence like a criterion Mendeleyev wrote on his project a table in which the periods were fill with thevalences, which increase following a harmonic form on the periods. 
The English chemist Henry Moseley discovered that atoms of each element have a unique number of protons in their nucleus, been the equalnumber of protons to the atomic number of the atom. When Moseley planning elements in order of increasing atomic number and it was not in order of increasing atomic mass, as he did Mendeleyev, the...