Neon, a noble gas, is recognized for its vibrant reddish-orange glow in electric signs, despite being colorless and odorless in its natural state. This element is chemically inert, meaning it does not readily react with other substances. Though familiar to many through its distinctive light, neon is surprisingly rare on Earth.
Neon in Earth’s Atmosphere
Most neon on Earth resides in its atmosphere. This trace gas constitutes approximately 18.2 parts per million (ppm) by volume of dry air, or 0.0018% of the total atmospheric composition. Its unreactive nature allows it to persist stably.
Atmospheric neon originated primarily from Earth’s interior outgassing. Isotope studies indicate some was trapped in the mantle during the planet’s formation. Its presence testifies to its stability.
Neon in Subterranean Sources
Beyond the atmosphere, minute quantities of neon exist in subterranean environments, including trace amounts in Earth’s crust and mantle, often trapped in rock formations. Researchers study neon isotopes in volcanic emissions and basalt to understand Earth’s formation.
Neon can also be present in minor concentrations within natural gas deposits. These underground sources are negligible compared to the atmospheric reservoir and not commercially viable for extraction due to their low concentrations.
Why Neon is Rare on Earth and How It’s Obtained
Neon is the fifth most abundant element in the universe, yet scarce on Earth. This rarity stems from its light atomic weight and high volatility. Earth’s gravity is not strong enough to retain large quantities of such a light, non-reactive gas over geological timescales.
During Earth’s early, warm formation, much primordial neon escaped from planetesimals. Unlike other elements, neon does not form compounds that would anchor it to solids. Industrial production relies exclusively on its atmospheric presence.
Neon is primarily obtained through cryogenic fractional distillation of liquid air. This process cools air to extremely low temperatures until it liquefies. As liquid air warms, components vaporize at specific boiling points, allowing separation. Neon, with a boiling point of approximately -246 degrees Celsius, is among the first gases to boil off.
This industrial extraction is often a byproduct of air separation plants producing oxygen and nitrogen, common in industries like steel manufacturing. Further purification removes trace contaminants like helium. Large volumes of air must be processed to yield small amounts of this gas.