Development of the Periodic Table (I couldn't find the exact dates for all of these events so that is why they all say 1st Jan)
By lollyhong123
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Dobereiner grouped the known elements based on similaritys.
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it was found that certain elements could be grouped together.When arranged in order of atomic mass the elements usually ended up in groups of 3. The middle element in the triad had an atomic weight that was the average of the other two members.
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English chemist John Newlands (1837-1898), having arranged the 62 known elements in order of increasing atomic weights, noted that after interval of eight elements similar physical/chemical properties reappeared. Newlands was the first to formulate the concept of periodicity in the properties of the chemical elements. In 1863 he wrote a paper proposing the Law of Octaves.
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Russian chemist Dimitri Mendeleev (1834-1907) proposed arranging elements by atomic weights and properties.
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Mendeleev revised the 17-group table with eight columns. This table showed similarities in an entire network of vertical, horizontal, and diagonal relationships. The table contained gaps but Mendeleev predicted the discovery of new elements.
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Lord Rayleigh reported the discovery of a new gaseous element named argon. This element did not fit any of the known periodic groups and therefore raised questions about why it was an odd one out. They realised there must be more elements that fitted into a group with this one.
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William Ramsey followed by discovering the remainder of the inert gases and positioning them in the periodic table.
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Rayleigh (physics) and Ramsey (chemistry) were awarded Nobel prizes in 1904.
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In this year Mendeleev came within one vote of receiving the Nobel Prize in chemistry.
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When Moseley arranged the elements according to increasing atomic numbers and not atomic masses, some of the inconsistencies associated with Mendeleev's table were eliminated.
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The first inert gas compound was made in 1962 (xenon tetrafluoride) and many have been made since then. The inert gases are more commonly known as the Noble gases nowadays.
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Today All together there are 117 elements on the periodic table, 94 of which occur naturally on earth.
