Question #61a18
1 Answer
Feb 4, 2018
Tough to say - francium, if you are asking about naturally occurring elements. Otherwise, likely Californium
Explanation:
My choices above were based on a survey of a number of web sites like this one:
https://www.thoughtco.com/what-is-most-expensive-element-606625
Francium exists in nature, but at any given time, there is not enough available to enable it to be viewed! Only a "few" atoms have ever been gathered at one time.
Reports state that Californium has been synthesized only once since 1950.
