The_History_of_the_Periodic_Table_(Summary)

A history of the Periodic Table. During the 1800’s, we knew that about sixty elements existed, but there was no real organisation of these elements. An order was needed, so many different scintists contributed, with Dmitri Mendeleev finally managing to construct the modern periodic table. Antoine Laviosier was born in 1743 in France. He was the first person to discover hydrogen and oxygen. He classified the know elements at the tim into four groups: Elastic fluids - Light, heat, oxygen, nitrogen and hydrogen were included in this group. Non-metals - Sulfur, phosphorus, carbon, hydrochloric acid, hydrofluoric acid and boric acid. Metals - Silver, bismuth, cobalt, copper, tin, iron, manganese, mercury, molybdenum, nickle, gold, platinum, lead, tungsten and zinc, along with antimony and arsenic (which are not considered metals today). Earths - included lime, magnesium oxide (or magnesia), barium oxide (baryta), amuminum oxide (alumina) and silicone dioxide (silica). Johann Wolfgang Döbereiner was born in Germany in 1780. He discovered that there were certain trends in properties of some groups of elements, like that the atomic mass of lithium and potassium was close to the atomic mass of sodium. He found that there was a similar pattern with calcium, strontium and barium, with sulfur, selenium and tellurium, and also with chlorine, bromine and iodine. These sets of elements were called, “Dobereiner’s Triads”, as they were in groups of three. This gave other scientit’s a clue that relative atomic masses were important when arranging the elements. John Newlands was an English scientist, who had the idea of a law of octaves in 1864. He put all the elements known at the time into order of relative atomic mass, and found that each element was similar to the element eight places on. However, this law placed iron in the same group as oxygen and sulphur, both of which are non-metals, and so his table was not accepted by other scientists. It did not work for the fourth period with the transition metals. It worked for the elements with an atomic number less than 19 because eight electrons completes the outer shell. Dmitri Mendeleev was a Russian chemist born in 1834. He also arranged his table of the elements known at the time into the order of relative atomic mass, but also put them into groups of similar properties. He had gaps in his table, but he predicted that those gaps were meant for elements that had not been discovered at the time.