Strange elements tend to have properties that make them extremely difficult to study. For example, Copernicium has a half-life of only 29 seconds, and Francium would probably explode upon contacting the moisture in the air.
Key Facts In This Video
Gallium safely melts in human hands. (0:44)
Francium has never been visible to the naked eye. (3:08)
When sufficiently cooled, Helium becomes a superfluid that seemingly defies gravity. (6:10)