Question: what is the rarest element on earth

Daniel Parsons answered on 10 Nov 2014:

Well, this is a tricky question. Some elements as so rare that they only exist in experiments for very short periods of time and we don’t think they exist naturally anywhere on Earth. Of those that do exist naturally, the rarest is thought to be Astatine, but nobody s 100% sure. This element only lasts a few hours and is basically made when larger elements undergo radioactive decay – that is their atoms are unstable and fall apart over time. Some estimates are that only 1 gram of Astatine exists on Earth at any one time. That is quite a bit less than a spoonful of sugar – pretty rare…