Neon
Neon is the noble gas that gives signs their famous glow, its distinctive orange-red light has lit up city streets and shop windows since the 1910s. Under normal conditions it is a completely colourless, odourless gas, but pass an electric current through it and it bursts into vivid colour.
- Atomic Number1010 protons, 10 electrons
- Atomic Mass20.180 uAbout 20× heavier than hydrogen
- State at Room TempGascolourless, odourless gas
- Density0.0008999 g/cm³Denser than air but still a gas
- Melting / Boiling-248.6°C / -246.1°CLiquefies at −246°C
- Discovered1898Ramsay & Travers, 1898
How does neon compare to the other noble gases in mass?
Neon is the second lightest noble gas. Each noble gas is notably heavier than the one above it.
Neon at 20 atomic mass units is five times heavier than helium (4 u) and half the mass of argon (40 u). Despite these differences, all noble gases behave similarly, almost completely inert with full outer electron shells.
What is neon?
Neon is a noble gas in Group 18 of the periodic table. Its atoms have ten protons and ten electrons, filling its first two electron shells completely. That completely filled outer shell makes neon extremely stable, it will not react with any other element under any ordinary conditions, and even under extraordinary ones. Of all the noble gases, neon has the smallest temperature range in which it is liquid, and it forms no confirmed chemical compounds at all.
Neon gets its name from the Greek word neos, meaning new. When William Ramsay and Morris Travers discovered it in 1898, it was genuinely new, isolated from liquefied air just weeks after they had discovered krypton. Ramsay's young son reportedly suggested the name after his father described their discovery as "a new gas".
Where you find neon
In space
Neon is the fifth most abundant element in the universe, produced in large amounts inside massive stars. Our Sun contains a significant amount of neon, though less than helium. On Earth, neon is extremely rare because, like helium, it is too light and unreactive to be permanently held by Earth's gravity.
On Earth
Neon makes up just 18 parts per million of the air, tiny, but enough to extract commercially by cooling air until it liquefies and warming it back up again, collecting each gas as it boils off at its own temperature.
- The atmosphere. Earth's air is approx. 0.0018% neon. A cubic metre of air contains approx. 18 millilitres of neon gas.
- Industrial air separation plants. Neon is separated from air by fractional distillation. Ukraine and the United States are among the world's largest producers, supplying the semiconductor industry.
How we use neon
- Neon signs. When an electric current passes through neon gas in a sealed glass tube, electrons collide with neon atoms and make them emit a distinctive orange-red light. Neon signs have been a landmark of city nightlife for over a century.
- Helium-neon lasers. This was one of the first continuously operating lasers ever built, invented in 1960. It produces a characteristic red beam used in supermarket barcode scanners, laser levels and physics demonstrations.
- Semiconductor manufacturing. High-purity neon is used in excimer lasers that etch the microscopic patterns onto computer chips. A neon shortage in 2022 drove up chip production costs worldwide.
- Cryogenic cooling. Liquid neon, at −246°C, cools equipment that needs temperatures between those achievable with liquid nitrogen and liquid helium.
How it was discovered
Neon was discovered in London in 1898 by William Ramsay and his student Morris Travers. They had just found krypton by carefully evaporating liquid argon and collecting what remained. They then turned their attention to the lighter fraction of liquid air, evaporating from the top and collecting the first gas to boil off. The vivid orange-red light it produced in a discharge tube was so striking that Travers wrote later that "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget".
Deeper dive: the noble gases and why Group 18 was hidden for so long
Group 18: the noble gases, was completely unknown to chemists before 1894. The periodic table had been constructed without them because no one knew they existed. Argon was the first discovered, when Lord Rayleigh and William Ramsay noticed that nitrogen extracted from air was very slightly denser than nitrogen made from compounds. The extra mass was argon. Within four years, Ramsay and Travers had found neon, krypton and xenon as well, an extraordinary burst of discovery.
All noble gases have a complete outer electron shell: helium has 2 electrons (filling its first shell), and all others have 8 electrons in their outermost shell (an octet). This configuration is so stable that noble gases have virtually no tendency to form chemical bonds at all. Chemists call atoms with complete outer shells "satisfied", they have nothing to gain from bonding.
The discovery of the noble gases forced a reorganisation of the periodic table. Mendeleev's original table had no place for them. Their addition as Group 0 (now Group 18) actually strengthened the periodic law by showing that chemical properties repeat with atomic number in an even more complete pattern than Mendeleev had suspected.
Neon is a truly inert element that lights up the world whenever electricity passes through it. Moving along the periodic table, the next element with eleven protons is sodium, an alkali metal so reactive it catches fire in water.