Question

What is the rarest element on Earth ?

Answer 1

1. Rare earth elements are the elements of any metallic series whose oxides are classed.
2. These are mostly the elements of lanthanide series.
3. The rarest element on the Earth is Astatine(At).
4. Its atomic number is 85.
5. It is obtained by the decay product of heavier elements.
6. The decay of Uranium and Thorium gives Astatine.
7. ${\mathrm{t}}_{1/2}$ for Astatine is 8.1 hrs.
8. Atomic mass for this element is 210.
9. It is a radioactive element.