Scientists
Published on Nov 20, 2015
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PRESENTATION OUTLINE
CONTRIBUTIONS
OF THE FOLLOWING SCIENTISTS
LAVOISIER
(1770-1789)
CONTRIBUTION:
Wrote the first extensive list of elements containing 33 elements. Distinguished between metals and non-metals.
DOBEREINER
(1829)
CONTRIBUTION:
Developed 'triads', groups of 3 elements with similar properties.
Lithium, sodium & potassium formed a triad.
Calcium, strontium & barium formed a triad.
Chlorine, bromine & iodine formed a triad.
CHANCOURTOIS
(1820-1886)
CONTRIBUTION:
Alexandre Béguyer de Chancourtois was the first person to list the known elements in order of increasing weight of their atoms.
NEWLANDS
(1864)
CONTRIBUTION:
The known elements (>60) 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'.
MENDELEEV
(1869)
CONTRIBUTION:
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.
RAMSAY
(1894)
