At the middle of the 19th century, 63 chemical elements were known to science. Before Mendeleev’s discovery, attempts at arranging them in some logical way were made by Johann Doebereiner (1829 ...

This year we celebrate the 150 th anniversary of Mendeleev’s achievement in formulating the structure of the periodic table that we use today. He announced his structure in 1869, but the challenge of ...

Existing explanations about how and when levels of gases changed in the ancient atmosphere are challenged by: Mendeleev left gaps where he predicted that elements, not discovered at the time ...