Contributions to Periodic table

Lavoiser Wrote the first extensive list of elements containing 33 elements. Distinguished between metals and non-metals.

Döbereiner Developed 'triads', groups of 3 elements with similar properties. Lithium, sodium and potassium formed a triad. Calcium, strontium and barium formed a triad. Chlorine, bromine and iodine formed a triad.

Newlands 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 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.

Meyer Compiled a Periodic Table of 56 elements based on the periodicity of properties such as molar volume when arranged in order of atomic weight.

Seaborg Synthesised transuranic elements (the elements after uranium in the periodic table)