Neon
noble gasProperties
| Property | Value |
|---|---|
| Atomic Mass | 20.18 amu |
| Category | noble gas |
| Group | 18 |
| Period | 2 |
| Electron Configuration | 1s2 2s2 2p6 |
| Oxidation States | 0 |
| Melting Point | 24.56 K (-248.6 °C) |
| Boiling Point | 27.104 K (-246.0 °C) |
| Density | 0.0008999 g/cm³ |
| Discovered By | William Ramsay (1898) |
About Neon
Neon has the cleanest closed-shell configuration on the periodic table: 1s² 2s² 2p⁶, ionization energy 21.6 eV, electron affinity essentially zero. No one has ever made a stable neutral compound of it, and that inertness is what makes the rest of its story possible. Pass a few hundred volts through a Geissler tube of low-pressure Ne and the 2p⁶ electrons get kicked into excited states that relax through about a dozen lines in the orange-red — the unmistakable 640 nm glow that Georges Claude commercialized into signage starting in 1910. Ramsay and Travers had isolated the gas just twelve years earlier by fractionally distilling liquid air, which is still how it's produced today. Neon makes up 18 ppm of the atmosphere but each cryogenic air-separation plant only captures a few hundred kilograms a year, which is why the gas costs roughly 50× as much as argon. Its 27 K boiling point also makes it a useful cryogen in the awkward gap between liquid hydrogen and liquid nitrogen.
Fun Fact
Despite its association with colorful signs, neon itself only glows reddish-orange — the other colors in 'neon signs' actually come from different gases like argon (lavender), mercury vapor (blue), or phosphor coatings on the glass tubes.
Common Uses
- Red-orange glow discharge tubes for signage and indicator lamps
- Excimer laser fill gas (ArF, KrF) for semiconductor photolithography
- Helium-neon lasers at 632.8 nm for alignment and interferometry
- Cryogenic refrigerant between liquid hydrogen and liquid nitrogen
- High-voltage surge arresters and starter tubes