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Jan 1, 1000
Prior to written history
Gold, Silver, Copper, Lead, Tin, Mercury were known at this point -
First element discovered via scientific method
First element discovered via scientific method Hennig Brand the element was Phosphorus -
Elements begin to be grouped
Johann Dobereiner began to group elements with similar properties into traids, made a halogen and an alkali traid -
Atomic weights
A.E. Beguyer de Chancourtois first person to make use of atomic weights to show that elements were arranged according to their weight and similar elements occurring at regular intervals, it was displayed as a continuous sprirl around a cyclinder and dived into 16 parts -
Law of octaves
John Newlands proposed the law of octaves, stating that elements repated their chemical properties every eighth element -
Dmitri Ivanovich Mendeleev
Dmitri Ivanovich Mendeleev came out with his work ‘On the Relationship of the Properties of the Elements to their Atomic weights’ many elements were out of order because their accepted weight at the time was incorrect, he predicted unknown elements ( gallium, scandium and germanium) and later found that these predictions were quite close to what would be found later -
Argon
Lord Rayleigh discovered argon which didn’t match any other known element at the time. -
Period: to
Perodic table development
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Ernest Rutherford
Ernest Rutherford published work which led to the determination of nuclear charge via the scattering of alpha particles by heavy atom nuclei -
A. van den Broek
A. van den Broek propsed that atomic weight of an element was close to the charge on an atom, the charge became termed as the atomic number and would be used to number the elements on the periodic table. -
1913
Henry Moseley discovered isotopes and showed that atomic weight wasn’t the significant part in the periodic law as those before had thought -
Glenn Seaborg
Glenn Seaborg discovered all the transuranic elements from 94 to 102 starting with plutonium in 1940, he also reconfigured the periodic table to place the actinide series below the lanthanide series, element 106 was named in his honour (seaborgium)