Which Noble Gases Are Used in Lighting?

• Neon lights are tubes filled with inert gas. Jupiterimages/Photos.com/Getty Images

  Noble gases are elements under the last column or group of the periodic table. Since their outermost electron shells contain a full complement of electrons, noble gases are inert or nonreactive. Fluorescent lights and neon signs often use tubes filled with noble gases with the exception of radon, which is radioactive and thus dangerous to handle. The color of the light depends on the type of gas and the type of coating.

Neon

• Neon is the 10th element of the periodic table and the most inert of the noble gases. Once widely used in advertising signs and displays, it gave its name to neon signs. All neon signs don't use neon, but the first neon signs did. In the absence of a phosphor coating on the tube, neon glows an orange color when current is applied.

Argon

• Argon is the 18th element of the periodic table, so atoms of argon are larger and heavier than atoms of neon. Fluorescent lights often use a mixture of argon and mercury vapor. In the absence of a phosphor coating, argon lights are lavender-colored. Argon is also a common gas in neon signs.

Xenon

• Xenon is the 54th element of the periodic table. It is heavier than neon, argon or krypton. Xenon lights exude a gray or pale blue gray color. Flash lamps in photography use xenon, as do arc lamps and strobe lights.

Krypton

• Krypton is the 36th element of the periodic table, so it's heavier than neon or argon. Krypton lights are gray or gray-green in color. According to the Los Alamos National Laboratory, it's rare to see krypton in lighting because it's expensive. It does, however, find use in some photographic flash bulbs.

Helium

• Helium is the lightest of the noble gases and the second most abundant element in the universe. It's so light that it easily escapes from Earth's gravity. Most of the helium present in Earth's crust forms from the radioactive decay of heavier elements. Helium lights are orange-white. Artists sometimes use helium in neon signs for art projects, but it's more common in lasers and other non-lighting applications.