When the Russian chemist Dmitri Mendeleev published his periodic table of elements in 1869, there were just fifty-nine entries on it. The table grouped those elements—hydrogen, oxygen, and carbon, ...

Supernovae and some stars that aren’t like our present-day Sun create radioactive elements not found in our solar system.

Researchers have for the first time examined in detail a compound of einsteinium (Es). Einsteinium is one of the synthetic elements--elements not found in nature. It is also the heaviest element ...

Californium is a synthetic, radioactive element not found in nature. It is an actinide: one of 15 radioactive, metallic elements found at the bottom of the periodic table. The pure metal is ...