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Period: to
The Development of the Periodic Table
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John Dobereiner (Germany)
(1828~1829)
Developed 'triads', groups of 3 elements with similar properties.
- Li, Na & P formed a triad.
- Ca, St & Ba formed a triad.
- Cl B & I formed a triad. -
John Newlands (British)
- The known elements of 56 were arranged in order of atomic weights and observed similarities between the first and ninth elements, the second and tenth elements etc.
- He proposed the 'Law of Octaves'.
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Demitri Mendeleev
Produced a table based on atomic weights but arranged 'periodically' with elements with similar properties under each other. Gaps were left for elements that were unknown at that time and their properties predicted (the elements were gallium, scandium and germanium). The order of elements was re-arranged if their properties dictated it, eg, tellerium is heavier than iodine but comes before it in the Periodic Table. -
Lothar Meyer (Germany)
Compiled a Periodic Table of 56 elements based on the periodicity of properties such as molar volume when arranged in order of atomic weight. -
Lord Rayleigh (John William Strutt, British)
Reported the discovery of a new gaseous element named argon which proved to be chemically inert. -
William Ramsey (Scotland)
Discovered the Noble Gases. -
Henry Mosley (British)
Determined the atomic number of each of the elements.
He modified the 'Periodic Law' to read that the properties of the elements vary periodically with their atomic numbers. -
Henry Moseley
Predicted that there were 3 unknown elements between aluminium and gold and concluded there were only 92 elements up to and including uranium.
"Moseley's Law" - picture -
Glenn Seaborg (USA)
-Synthesised transuranic elements (the elements after uranium in the periodic table)
-Discovered 94 to 102th elements
-106th element named a Seaborgium(Sg) in his honor
