The list of all noble gases includes helium, neon, argon, krypton, xenon, and radon. Each of the noble gases (except radon) and their characteristic glow with an electrical discharge. Argon glows blue, and krypton glows a whitish purple. Each noble gas glows a different color: for example, neon is reddish orange, like in neon signs. If an electrical discharge passes through a noble gas at low pressure, the gas will glow, as seen in the image below. This is because they easily emit electromagnetic radiation. Noble gases are often used in fluorescent lighting and discharge lamps. Radon is a product of the radioactive decomposition of radium compounds. Xenon is an anesthetic, albeit a costly one. Both helium and neon are used as cryogenic refrigerants. Argon is used in incandescent lamps, and neon is used in signs. Most helium comes from natural gas, and some people worry that we may run out of helium one day. Helium’s uses include blimps and balloons, as well as deep-sea diving (aka technical diving), mixed with oxygen. Helium is the only element that will not freeze at atmospheric pressure, no matter how low the temperature. Unlike the halogens, noble gases are monatomic, meaning that they do not form molecules of multiple atoms – each “molecule” of the gas is just a single atom. They are all very close to being ideal gases. The noble gases all have very low melting and boiling points, due to their weak intermolecular forces. Because of their nonreactivity, one organic chemist even referred to them as the “lazy elements.” However, Neil Bartlett showed us another side to these elements in 1962 by discovering a compound of xenon. These monatomic gases also conduct electricity and can fluoresce. The noble gases are tasteless, odorless, colorless, nonflammable, and mostly nonreactive. Most of this argon in the air arises from the decay of radioactive potassium-40. In fact, air is 0.934% argon, while the other group 18 elements are present in much smaller quantities. They are members of group 18, the last group on the periodic table.Īll of the noble gases occur in the atmosphere. The noble gases are a group of six inert (nonreactive) gases on the far right side of the periodic table.

Color coded periodic table with gases