Earth and moon

First posted on FB 17/01/2020 A pair of elements today, selenium and tellurium, adjacent in Group 16. Before Mendeleev proposed his Periodic Table, other scientists had put forward similar ideas. In 1862, Alexandre-Emile Beguyer de Chancourtois proposed a helical arrangement with the elements in order of relative atomic mass and those with similar properties aligned vertically.Continue reading “Earth and moon”