Question

What are the two radioactive elements are not found observable quantities in nature?

Answer 1

These radioactive elements are Tritium and Plutonium. They occur naturally in trace amounts (extremely small). Tritium is extremely rare on the Earth, its trace amounts are formed by the interaction of the atmosphere with cosmic rays. Plutonium-244 ( the most stable isotope of Plutonium) have a half-life of about 80 million years. Thus, it is just barely stable enough that some of it has remained from the Earth’s formation.