It has always been MYSTERIOUS and ELUSIVE but it just was MEASURED FOR THE VERY FIRST TIME!
A radioactive metal of the actinide series.
What is actinide you ask?
Actinide
Any element of the Actinide series
Actinide Series
The series of radioactive elements that starts with actinium and ends with lawrencium
Actinium
A silver white radioactive metallic element that glows blue in the dark resembling the rare earths in chemical behavior and valence
Valence
The quality that determines the number of atoms or groups with which any single atom or group will unite chemically
I was not as smart as you. I did not know that ELEMENT 99 represented anything other than an internet moniker. Now I know. EINSTEINIUM. Mysterious.
Kinda cool don'tcha think?