Einsteinium

**Definition:** A man-made radioactive actinide with atomic symbol Es, and atomic number 99. Its known isotopes range in mass number from 240-258. Its valence can be +2 or +3. Einsteinium was originally discovered in the debris from a thermonuclear explosion in 1952.

**Tree numbers:** - D01.268.271.100.250 - D01.268.556.244 - D01.496.749.305.100.250 - D01.552.020.337 - D01.552.544.244