Krypton - a cryptic trace in air we breathe

 Krypton - a cryptic trace in air we breathe

Krypton (Kr) is in the heavier half on naturally occuring noble gases, being a larger atom than argon and smaller than xenon. It's properties are, for the most part, similar to the rest. But since 18th group's reactivity increases, as we go down, krypton is able to form a couple of obscure compounds. 

It can be found naturally occuring in atmospheric air, from which it's extracted to be used industrially. Air contains just about 1 part per million of krypton, which would be about the same concentration as 2 liters of soda in an Olympic swimming pool. And yet we still use it to fill random lightbulbs!

A 10x40mm glass ampoule of krypton gas.

As it is often the case, most element collectors will have to accept that there are not all that many samples that can be acquired - the most widely available ones are glass ampoules filled with krypton gas, usually with a very low pressure inside. That makes them able to glow with a bluish or brownish white color when excited with electricity.

Krypton spectrum in a discharge tube by Alchemist-hp on Wikipedia.

Such simple tubes can be shaped into different forms, most notably the letters making up the Kr symbol, but these samples aren't a cheap sight to behold!

Krypton is widely used in lighting. Whether it's plain space ilumination or a specialized laser, this gas can do it all. Some kinds of lasers use ionized krypton plasma to amplify the optical power of a beam.

When krypton gas is forced to react with fluorine by an external source on energy, an unstable krypton fluoride complex is formed. Such particle can reduce it's energy levels, causing an emission of ultraviolet light wave. This weird behavior is tamed to be used in so called exciplex lasers. Also, I have no idea if what I just wrote is factually correct - I don't know much about lasers, so sorry if I made any expert's eyes bleed!

Krypton filled flashlight bulb.

Outside the premade samples, krypton gas can be found relatively easy inside these small flashlight bulbs. The rare gas inside is supposed to make them last longer by reducing the rate at which tungsten inside evaporates. Unfortunately (or fortunately?), due to LEDs being so efficient and widely available, such bulbs are getting harder to find in normal hardware stores. 

Not much more to say about krypton in the "holdable" department, but did you know that in it's frozen form, krypton has the same crystalline structure as aluminum, copper or austenitic steels? That doesn't mean it would make for a good construction material though - especially with melting and boiling point being respectively around 116 K and 120 K.

Multiple heavy and radioactive isotopes of krypton are produced as a result of nuclear fission of uranium-235. These all have relatively large neutron absorption cross-sections, thus are considered reactor poisons to some extent. Multiple unstable isotopes of krypton occur naturally in air as traces, but fear not - there is no chance to get hurt by them!