Astatine is a rare and radioactive element with the chemical symbol At and atomic number 85. It belongs to the halogen group, which includes elements like fluorine, chlorine, and bromine. Astatine is found in trace amounts in nature, primarily produced through the decay of heavier elements. Its isotopes have very short half-lives, making it difficult to study. Due to its radioactivity, astatine has limited practical applications. However, researchers are exploring its potential use in targeted alpha-particle cancer therapy. The element's scarcity and instability pose challenges for further research and development in this area.