Charles Janet

Charles Janet (French: [ʒanɛ]; 15 June 1849 – 7 February 1932) was a French engineer, company director, inventor and biologist. He is also known for his innovative left-step presentation of the periodic table of chemical elements.

Janet graduated from the École des Mines and worked for some years in munitions. He then married the daughter of the owner of a manufacturing company and worked for it for the rest of his life, finding time for research in various branches of science. His collection of 40,000 fossils and other specimens was unfortunately dispersed after his death. His studies of the morphology of the head of ants, wasps and bees, and his micrographs were of remarkable quality. He also worked on plant biology and finally wrote a series of papers on evolution. He was a prolific inventor and designed much of his own equipment, including the formicarium, in which an ant colony is made visible by being formed between two panes of glass. In 1927 he turned his attention to the periodic table and wrote a series of six articles in French, which were privately printed and never widely circulated. His only article in English was poorly edited and gave a confused idea of his thinking.

Janet started from the fact that the series of chemical elements is a continuous sequence, which he represented as a helix traced on the surfaces of four nested cylinders. By various geometrical transformations he derived several striking designs, one of which is his "left-step Periodic Table", in which hydrogen and helium are placed above lithium and beryllium. It was only later that he realized that his arrangement agreed perfectly with quantum theory and the electronic structure of the atom. He placed the actinides under the lanthanides twenty years before Glenn Seaborg, and he continued the series to element 120.

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