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 | N/A |
| 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
1s2 2s2 2p6
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| Total | 8 | 10 | ||
Isotopes of Neon
Neon has three stable isotopes: neon-20 (90.48%), neon-22 (9.25%), and neon-21 (0.27%). The neon-21/neon-22 ratio in geological samples is used as a tracer for mantle melting and ocean-crust interactions in geochemistry.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Neon-20 | ²₀Ne | 10 | 10 | 90.48% | Stable |
| Neon-21 | ²¹Ne | 10 | 11 | 0.27% | Stable |
| Neon-22 | ²²Ne | 10 | 12 | 9.25% | Stable |
Abundance & Occurrence
Neon is extremely rare on Earth — present at only about 18.2 parts per million by volume in the atmosphere, making it far less abundant than argon (9,300 ppm) or helium (5.2 ppm). In Earth's crust it is virtually absent (0.0005 ppm). In the universe, however, neon is the fifth most abundant element at approximately 1,300 ppm by mass, produced in large quantities during stellar nucleosynthesis (the neon-burning process in massive stars). Commercial neon is extracted solely by fractional distillation of liquid air.
Earth's Atmosphere — Noble Gas Concentrations (ppm by vol.)
Universe — Selected Element Abundances (ppm by mass)
Discovery & History
Safety & Handling
- Non-toxic and chemically inert: Neon forms no known stable chemical compounds and is physiologically inert. It poses no toxicological hazard and is not a carcinogen, mutagen, or reproductive toxicant.
- Asphyxiation in enclosed spaces: Like all noble gases, neon is an asphyxiant at high concentrations. In a poorly ventilated area a neon leak can displace oxygen silently — the gas is colourless and odourless, and oxygen deficiency may cause rapid loss of consciousness without warning. Ensure adequate ventilation wherever neon cylinders or cryogenic containers are stored.
- Cryogenic hazards (liquid neon): Liquid neon boils at −246°C and causes severe cryogenic burns on skin or eye contact. Use thermally insulated cryogenic gloves, face shields, and appropriate cryogenic storage dewar flasks. Liquid neon produces very large volumes of gas upon evaporation — never seal it in an unvented container.
- High-pressure cylinder safety: Commercial neon is supplied as a compressed gas in steel cylinders at up to 200 bar. Cylinders must be stored secured upright, away from heat sources, and protected from impact. Always use the correct pressure regulator rated for inert gas service.
Neon in the Real World
Real-World Uses
- Neon signs and lighting — Sealed glass tubes filled with neon gas glow bright red-orange when an electric discharge is passed through them. Since their introduction by Georges Claude in the 1910s, neon signs have been central to commercial advertising worldwide. Other colours in so-called neon signs are produced by different gases (argon for blue-purple) or fluorescent coatings, but pure neon produces only the iconic red-orange hue.
- High-voltage indicators — Neon indicator lamps (neon glow lamps) are used in electronic circuits as low-current power-on indicators, phase indicators, and overvoltage protection components. They operate across a wide voltage range and are essentially indestructible, making them common in industrial control panels and vintage test equipment.
- Cryogenic refrigerant — Liquid neon has a boiling point of −246°C and a refrigerating capacity per unit volume about 40 times that of liquid helium. It is used as a cryogenic coolant for superconducting magnets and sensors in applications where helium supply is a concern, particularly after supply chain disruptions highlighted helium's scarcity.
- Helium-neon (He-Ne) laser gain medium — In He-Ne lasers, neon atoms serve as the laser gain medium. Helium atoms excited by electrical discharge transfer energy to neon via collisions, producing population inversion and laser emission at 632.8 nm (red) or other wavelengths. He-Ne lasers are used in barcode scanners, holography, interferometry, and alignment tools.
- Plasma display panels — Neon (and xenon) gas mixtures generate UV photons in plasma display panels (PDPs) when excited by electrical discharge. These UV photons excite phosphor coatings on each sub-pixel to emit red, green, or blue visible light. While largely superseded by OLED and LCD technology, PDPs were a major display technology in the 2000s.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
Why do neon signs glow red-orange?
When a high voltage is applied across a sealed glass tube containing neon gas, the electric field accelerates free electrons that collide with neon atoms, exciting their electrons to higher energy levels. When those electrons return to their ground state they release photons of specific wavelengths — mostly in the red to orange range (585–703 nm) of the visible spectrum. This characteristic glow is unique to neon; other gases produce other colours. Many ‘neon signs’ actually use argon or other gases with phosphor coatings to produce blue, green, or white light.
Why is neon chemically inert?
Neon has a completely filled outer electron shell (1s² 2s² 2p⁶), giving it the maximum stable configuration of 8 electrons in its valence shell. This full octet means neon has no tendency to gain, lose, or share electrons in chemical bonds. Unlike the heavier noble gases xenon and krypton, neon's electrons are too tightly bound to participate in any known stable compounds even under extreme conditions.
Where does neon come from?
Neon is produced by fractional distillation of liquid air. It boils at −246°C, between nitrogen (−196°C) and helium (−269°C), allowing it to be separated in a cryogenic air separation plant. Neon is rare in Earth's atmosphere (18 ppm by volume) but much more abundant in the universe, where it is the fifth most abundant element. The vast majority of commercial neon supply historically came from air separation plants in Ukraine and Russia.
How was neon discovered?
Neon was discovered in 1898 by William Ramsay and Morris Travers in London. After isolating argon and helium, they suspected additional noble gases existed. By fractionally distilling liquid argon, they obtained a new gas with a bright crimson spectral line never seen before — naming it neon from the Greek neos, meaning ‘new.’ Ramsay received the 1904 Nobel Prize in Chemistry for his work on the noble gases.
Is neon used in lasers?
Yes. The helium-neon (He-Ne) laser, first demonstrated in 1960, was the first continuously operating gas laser and remains one of the most widely used. A mixture of helium (around 90%) and neon (around 10%) is excited by electrical discharge; helium atoms transfer energy to neon atoms, producing laser emission at 632.8 nm (red), 543.5 nm (green), or several infrared wavelengths depending on the mirror configuration. He-Ne lasers are used in barcode scanners, holography, and optical alignment.