Astatine is a radioactive chemical element. Its atomic number is 85 and its chemical symbol is At. It is heaviest halogin created through radioactive decay in nature. It is found in small amounts. It was discovered in 1940 by the concerted efforts of Dale R. Carson an American physicist, K.R. MacKenzie an American physicist and Emilio Segre an Italian physicist. Emilio Segre won the Noble Prize in 1959 for his great achievements in the field of Physics.