Tennessine

Tennessine is a synthetic, highly radioactive element whose atoms have been produced only in tiny numbers and survive for milliseconds before decaying. It was first made by fusing calcium and berkelium nuclei in a particle accelerator. Because so few atoms have been produced and they decay so quickly, its physical and chemical properties have not been directly measured; predictions suggest it may behave differently from lighter halogens. Tennessine has no practical applications, and its production and study are limited to scientific research.