Neon is a fascinating element, widely recognized by the vibrant glow of city signs. Classified as a noble gas, Neon (Ne) sits on the far right of the periodic table and is known for its extreme chemical inertness. It is colorless and odorless in its natural gaseous state. However, it becomes intensely luminous when an electrical current is passed through it, a characteristic that makes it instantly recognizable.
The History of Its Discovery
The element was discovered in 1898 by British chemists Sir William Ramsay and Morris Travers at University College London. They investigated the components of dry air, following the earlier isolation of Argon. They used fractional distillation, cooling air until it liquefied and then slowly warming it to separate the constituent gases based on their unique boiling points.
After removing known gases like nitrogen, oxygen, and argon, a tiny remaining fraction was isolated. When subjected to an electrical discharge, this residual gas emitted a brilliant, never-before-seen red light. This distinctive spectroscopic signature confirmed the existence of a new element, which Ramsay named “neon” from the Greek word neos, meaning “new.”
Why Neon Lights Glow Red-Orange
The iconic red-orange light results from neon’s atomic structure and electrical discharge. A high voltage is applied across the neon gas within a sealed glass tube, causing electrons to accelerate and collide with neutral neon atoms. These collisions transfer energy, temporarily boosting the neon atoms’ electrons to a higher energy level, making the atoms “excited.”
The excited electrons quickly fall back to their lower energy levels. As they return, they release the absorbed energy as photons, or particles of light. The specific energy drop in neon atoms corresponds precisely to photons in the red-orange region of the visible light spectrum, giving pure neon its characteristic hue.
The term “neon light” is a general descriptor for all gas-discharge signs, but pure neon gas produces only the red-orange color. Other colors are achieved by using different noble gases, such as argon for blue or krypton for a white-blue shade. Colors are also created by coating the inside of the glass tube with phosphors, which absorb the ultraviolet light produced by the gas discharge and re-emit it as a different color.
Essential Roles Beyond Illumination
Neon’s applications extend beyond decorative signage, utilizing its inert nature and unique spectral properties.
Semiconductor Manufacturing
Ultra-high-purity neon is a major component in excimer lasers used for photolithography. This process precisely etches microscopic circuits onto silicon wafers during semiconductor manufacturing.
Electrical Devices
The gas is also used in devices requiring electrical stability, such as high-voltage indicators and lightning arrestors. Neon acts as an insulator until a specific high voltage is reached, at which point it rapidly ionizes and conducts the excess electrical current to safely discharge it.
Lasers and Cryogenics
Another use is in the helium-neon (HeNe) laser, which produces a stable, visible red beam used in barcode scanners, interferometry, and alignment systems. Liquid neon, with a boiling point of approximately -246 degrees Celsius, is a potent cryogenic refrigerant. Although less common than liquid helium, liquid neon offers more than 40 times the refrigerating capacity per unit volume than liquid helium, making it valuable for intense cooling needs. Its triple point temperature is also used as a fixed reference point on the International Temperature Scale of 1990.
The Scarcity and Extraction Process
Neon is the fifth most abundant element in the universe, yet it is extremely scarce on Earth, comprising only about 18 parts per million (0.0018%) of the atmosphere. Its light atomic mass and chemical inertness prevented it from being gravitationally captured during Earth’s formation, resulting in low terrestrial abundance. Since neon does not form chemical compounds, the atmosphere is its only commercial source.
Extracting neon is an energy-intensive process known as cryogenic fractional distillation of air. Air is first liquefied at extremely low temperatures, and neon is then separated from other gases like oxygen and nitrogen based on its distinct boiling point. This process is typically performed as a by-product of large-scale oxygen production plants, often associated with the steel industry. The trace quantities and high energy required for separation make purified neon an expensive industrial gas necessary for advanced manufacturing, particularly in the semiconductor industry.