Noble gas refers to any of a group of seven chemical elements . Six of these elements— helium (chemical symbol, He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn)—occur naturally and can be found in the atmosphere. These elements were first isolated and studied between 1894 and 1900. The seventh noble gas, oganesson (Og), has been produced in laboratories in very small quantities and little is known about its properties. There is no evidence that oganesson exists in nature.
Unlike most gaseous elements, the noble gases are monatomic—that is, they occur as single atoms instead of in molecules of two or more atoms. The atoms of noble gases have stable configurations (arrangements) of electrons . Therefore, the atoms do not, under normal conditions, gain or lose electrons or share electrons with other elements. The gases are called “noble gases” or inert gases because they do not readily react with other elements. But most of the noble gases will form certain compounds under specialized conditions.
The noble gases have various uses. Helium, neon, argon, krypton, and xenon are used as light sources in incandescent and gaseous-discharge lamps (see Electric light ). Some also are used in devices called gas lasers (see Laser (Kinds of lasers) ).
Argon and helium are used in a welding process called arc welding. They provide a chemically inactive atmosphere in which certain metals , such as aluminum, can be heated to their melting points without reacting chemically. Helium also is used in balloons, including those that carry scientific instruments high into the atmosphere, and in low-temperature research.
