Neon
Atomic Data
| Atomic Number | 10 |
| Symbol | Ne |
| Atomic Weight | 20.18 u |
| Density (STP) | 0.9002 g/L |
| Melting Point | −248.59 °C (24.56 K) |
| Boiling Point | −246.08 °C (27.07 K) |
| Electronegativity | — |
| Electron Config. | 1s2 2s2 2p6 |
| Oxidation States | 0 |
| Phase at STP | Gas |
| Category | Noble Gas |
| Period / Group | 2 / 18 |
| CAS Number | 7440-01-9 |
Electron Configuration
[He] 2s2 2p6
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| Total | 10 | 10 | ||
Abundance & Occurrence
Neon is present in Earth's crust at approximately 0.0005 ppm by mass and at approximately 1300 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Asphyxiation: Neon is a colourless, odourless inert gas; it displaces oxygen in confined or poorly ventilated spaces and can cause rapid unconsciousness and death at concentrations that reduce oxygen below safe levels.
- Pressurised cylinders: Neon is stored under high pressure; cylinders must be secured, kept away from heat, and handled with proper regulators — valve failure can cause rapid, uncontrolled release.
- Liquid neon: Liquid neon at −246 °C causes severe cryogenic burns on skin contact; rapid vaporisation in enclosed spaces can displace oxygen to dangerous levels.
Neon in the Real World
Real-World Uses
- Illuminated signs and lighting — Neon gas in sealed glass tubes emits a characteristic red-orange glow when electrically excited, used in neon signs; other noble gases and fluorescent coatings in the same tubes produce different colours.
- Helium-neon lasers — The He-Ne laser (632.8 nm red wavelength) was widely used in supermarket barcode scanners, laser printers, holography, and laboratory optics before being largely replaced by semiconductor diode lasers.
- High-voltage indicators — Small neon indicator lamps (such as the NE-2) glow at ~70–90 V AC and serve as mains-voltage indicators in power switches and circuit testers.
- Cryogenic research — Liquid neon (boiling point −246 °C) is used as a cryogenic coolant in research applications requiring temperatures between those accessible with liquid nitrogen and liquid helium.
- Plasma display research — Neon-xenon gas mixtures create the plasma that drives ultraviolet emission in plasma display panels (PDPs), which were used in flat-panel televisions before being superseded by LCD and OLED technology.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is neon used for?
Neon is best known for neon signs, where the gas in sealed glass tubes emits a characteristic red-orange glow when electrically excited. It is also used in helium-neon lasers, high-voltage indicator lamps, and as a cryogenic coolant in a temperature range inaccessible to cheaper nitrogen. Neon-xenon gas mixtures were used in plasma display panels.
Is neon truly inert?
Neon is the most chemically inert of all elements — even more so than helium. No stable neutral compound of neon has ever been synthesised under normal conditions, because neon’s filled valence electron shell gives it essentially zero chemical reactivity. Temporary van der Waals complexes with other atoms can be detected spectroscopically at very low temperatures, but these are not true chemical bonds.
Why does neon glow red in signs?
When an electric current passes through a sealed tube containing neon gas at low pressure, it excites neon atoms to higher energy electronic states. As the electrons fall back to lower energy levels, they release photons at specific wavelengths. For neon, these emission lines fall predominantly in the red and orange part of the visible spectrum (585–703 nm), producing the characteristic warm red-orange colour. Other gases produce different colours: argon gives blue-purple, helium gives yellow-white, and krypton gives yellow-green.
How was neon discovered?
Neon was discovered in 1898 by Sir William Ramsay and Morris Travers in London. After isolating argon (1894) and helium (1895), Ramsay and Travers liquefied crude argon and subjected the evaporating gas to spectroscopic analysis. A new bright-red spectral line appeared that matched no known element — this was neon (from the Greek neos, meaning 'new'). Krypton and xenon were discovered during the same series of experiments.