Tennessine (Ts), element 117, is a superheavy element with an estimated density of about 7.17 g/cm^3. It was synthesized in 2010 by a Russian-American collaboration that bombarded a berkelium target with calcium-48 beams in a heavy-ion accelerator; a single experiment yields only a few atoms, and every known isotope decays on a millisecond timescale. It does not occur in nature and cannot be accumulated into a weighable amount, so it has no industrial, civilian or medical use. It exists solely as an object of nuclear physics and superheavy-element chemistry research, used to test predicted properties at the halogen position of period 7.
Tennessine compounds have never actually been synthesized, let alone applied. Periodic-law extrapolation suggests it may form a hydrogen halide-like molecule with hydrogen and ionic salts with alkali metals, but these predictions exist only at the level of theoretical calculation. Superheavy chemistry today can only infer its behavior indirectly through single-atom gas-phase chromatography or solution tracer experiments; it enters no product.
