Xenon

Xenon is a colorless, odorless noble gas that rarely reacts with other substances. However, it can form compounds under suitable conditions, helping overturn the old idea that noble gases could never react. Tiny amounts occur naturally in Earth's atmosphere. Industry recovers xenon as a by-product when air is cooled into a liquid and separated to produce oxygen and nitrogen. Further separation concentrates and purifies the xenon. An electric current passing through xenon can produce intense light, making it useful in photographic flash lamps and cinema projectors. Xenon also serves as a propellant in spacecraft ion engines, which use electricity to accelerate charged atoms and create thrust.