Argon is a noble gas, an element found in Group 18 of the periodic table, characterized by its chemical inertness. It is the third most abundant gas in Earth’s atmosphere, making up approximately 0.934% of the air we breathe. In its natural state, whether as a gas, liquid, or solid, argon is colorless, odorless, and tasteless.
Argon’s Appearance and Properties
When an electric current is passed through it, argon displays a distinctive purplish-blue or violet glow. This visible emission occurs because the electrical energy excites argon atoms. Electrons within these atoms absorb energy and jump to higher energy levels, placing the atom in an excited state.
The excited state of these electrons is unstable. To return to a more stable, lower energy level, the electrons release the absorbed energy as photons, which are particles of light. The specific wavelengths of light emitted by argon atoms correspond to the energy differences between these electron energy levels, resulting in the characteristic purplish-blue or violet color. Despite their chemical inertness, argon atoms readily emit light when sufficient energy is supplied.
Where You Encounter Argon Visually
While naturally invisible, argon’s unique properties allow it to be seen in various applications when energized. In “neon” signs, for example, argon gas is specifically used to create blue or purple colors. This contrasts with pure neon gas, which produces a red-orange glow. Often, argon is combined with mercury vapor or internal phosphor coatings in these tubes to achieve a wider spectrum of hues, including greens, yellows, and whites.
Argon also plays a role in other lighting technologies. In incandescent light bulbs, argon gas fills the bulb to prevent the tungsten filament from rapidly oxidizing and burning out, significantly extending the bulb’s lifespan. In fluorescent lights, argon often acts as a starter gas, helping to initiate the electrical discharge that then energizes mercury vapor to produce ultraviolet light, which in turn excites a phosphor coating to create visible light.
Beyond lighting, plasma balls demonstrate argon’s glowing properties directly, as the gas inside the sphere emits a deep purple or pale blue-violet light when subjected to a high-voltage electric field. Argon is also used in insulated windows, where it is sealed between panes of glass. Here, it remains invisible but improves the window’s thermal insulation and helps prevent condensation, contributing to clearer views.