Enter a clue or pattern or both:
The Clue
Element #99 (11 letter answer)
The Answer
EINSTEINIUM
Tags
Notes
The answer EINSTEINIUM is so rare that it appears less than once every 2500 puzzles.
Definition
EINSTEINIUM as a noun:
1. (einsteinium, Es, E, atomic number 99) = a radioactive transuranic element produced by bombarding plutonium with neutrons