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Johaan Dobereiner grouped elements based on atomic weight.
Ca Sr Ba (40 + 137) ÷ 2 = 88
40 88 137
he noticed strotium fell exactly in the middle of calcium and barium. -
Alexandre , was the first to understand the physical properties of elements. in 1862 he published a list of all the known elements at the time. the list was a helical graph wrapped around a cylinder . elements with similar properties occupied positions on the same vertical line of cylinder .
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Johaan Dobereiner explained the law of the triads to other scientists who built on Dobereiner's ideas .
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Mendeleev's periodic table of 1869 contained 17 columns with two partial periods of seven elements each followed by two nearly complete periods . The table contained gaps but Mendeleev predicted the discovery of new elements.
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John Newlands was an english chemist. he noted down all 62 elements in order of atomic weights . he notice that after every 8 properties reapered. he was the first to notice the periocity of the elements .
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ramsey (chemist) + rayleigh (physist) were the first to dicover inert gasses . As this was a new dicovery they found that the periodic table didnt have these gasses so they positioned them into the correct groups .
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John Newlands wrote a paper on the law of octaves .
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In 1871 Mendeleev revised the 17-group table with eight columns (the eighth group consisted of transition elements). This table exhibited similarities not only in small units such as the triads, but showed similarities in an entire network of vertical, horizontal, and diagonal relationships.
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henry moseley subjected known elements to x-rays. He was able topick out the relationship between x-ray frequency and number of protons. he then arranged the elements in order of atomic number not mass. this cleared the incosistancy of mendeleev's periodic table.
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rayleigh discovered the very unreactive gas argon.
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Rayleigh (physics) and Ramsey (chemistry) were awarded Nobel prizes in 1904
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In 1906, Mendeleev came within one vote of receiving the Nobel Prize in chemistry
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this discovery helped moseley with his input of the periodic table.
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seaborg's discovery of the transuranium elements was the finalising piece to the puzzle for the periodic table , this final discovery gave the table the widely know shape that it holds today.
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In 1951 Seaborg was awarded the Nobel Prize in chemistry and element 106 was later named seaborgium (Sg) in his honor.