All practice pages/Interatomic theory/Elements
Element 54, a noble gas
A heavy noble gas that proved noble gases can react, now lighting car headlights and pushing spacecraft through space.
Period 5, group 18. The other noble gases are tinted, and every cell opens its own article.
A full valence shell, but its outer electrons sit far from the nucleus, so xenon can be forced to share them with fluorine and oxygen. It forms more compounds than any other noble gas.
About 0.09 parts per million of air, one of the rarest gases in the atmosphere, collected when air is liquefied and separated.
William Ramsay and Morris Travers found it in July 1898 in the residue of evaporated liquid air and named it from the Greek xenos, stranger. In 1962 Neil Bartlett made xenon hexafluoroplatinate, the first compound of a noble gas, overturning the belief that noble gases could not react.
Bright xenon lamps in car headlights, cinema projectors and camera flashes; ion thrusters on spacecraft such as NASA's Dawn probe; a general anesthetic; and large tanks of liquid xenon in underground detectors searching for dark matter.