The periodic table devised by Dmitri Mendeleev in 1869 had only seven groups, but Ramsay suspected the new element may belong to a hitherto unknown eighth group.

The periodic table stares down from the walls of just about every chemistry lab. The credit for its creation generally goes to Dimitri Mendeleev, a Russian chemist who in 1869 wrote out the known ...

THE annexed engraving is a copy, on a small scale, of a large diagram which I have used with advantage for some years in dealing with the periodic classification of the elements. It may prove of ...