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Antoine Lavoisier
Antoine Lavoisier formed the first very, extensive chart of the 33 elements known at the time. They were sorted into groups and metals were distinguished from non-metals. While many were in fact proper elements, the list included light as one of the elements, among a substance "caloric" which was proved to be fictitious. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown) -
Jöns Jakob Berzelius
Jöns Jakob Berzelius discovered several new elements such as cerium, selenium and thorium. In his laboratory, students also discovered lithium, vanadium and several rare earths. He determined the atomic weights of nearly all the elements known at the time and the number of elements he dealt with convinced him to create a simple, logical system of symbols for each element, similar to the one currently used. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown) -
Period: to
William Ramsay
William Ramsay discovered the Noble Gases. Argon was discovered when oxygen, nitrogen, water and carbon dioxide were removed from air. Helium was a decay product from uranium, and neon, krypton and xenon were also discovered. Ramsay realised that these elements were of a new group that was not on the periodic table. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown) -
Dmitri Mendeleev
The elements were arranged 'periodically' while being based on their atomic weights. Elements with similar properties were placed together and gaps for unknown elements were left and their properties predicted. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown) -
Henry Moseley
Henry Moseley determined the atomic number of each element, and understood that the properties of the element vary with their atomic numbers. Moseley altered the 'Periodic Law', which placed tellurium, iodine, argon, potassium, cobalt and nickel in their correct order. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown) -
John Newlands
Elements know at this time (>60) were sorted by their atomic weight and similarities between the first and ninth elements were observed. A pattern was distinguished, repeating the process with the second and tenth, and so on. This was named as the 'Law of Octaves'. (Note: This date is not accurate, only set to mark the year. Exact dates are unknown)
