Neon gas is used primarily to light up glass tubes in advertising displays.
Credit: Sorbis | Shutterstock
The gas that makes Las Vegas shine is one of the nobles — the noble gases, that is. Neon is one of six elements, found in the rightmost column of the Periodic Table, that are inert. Noble gases react very unwillingly, because the outermost shell of electrons orbiting the nucleus is full, giving these gases no incentive to swap electrons with other elements. As a result, there are very few compounds made with noble gases.
Like its noble gas comrades, neon is odorless and colorless. Under certain laboratory conditions, neon can form a compound with fluorine, but is otherwise nonreactive, according to the Thomas Jefferson National Accelerator Laboratory.
Just the facts
- Atomic number (number of protons in the nucleus): 10
- Atomic symbol (on the Periodic Table of Elements): Ne
- Atomic weight (average mass of the atom): 20.1797
- Density: 0.0008999 grams per cubic centimeter
- Phase at room temperature: gas
- Melting point: minus 415.46 degrees Fahrenheit (minus 248.59 degrees Celsius)
- Boiling point: minus 410.94 F (minus 246.08 C)
- Number of isotopes (atoms of the same element with a different number of neutrons): 18; three of which are stable
- Most common isotopes: neon-20 (natural abundance: 90.48 percent), neon-21 (natural abundance: 0.27 percent) and neon-22 (natural abundance: 9.25 percent)
Neon gets its name from the Greek word "neos," meaning "new." The gas was first isolated in 1898 by chemists William Ramsay and Morris Travers, who were busily discovering noble gases left and right by evaporating liquefied air, according to the Royal Society of Chemistry. They started with liquid argon, which, when evaporated, made krypton, which fits in the niche below argon on the Periodic Table. Suspecting there was another gas to be discovered, the researchers turned to solid argon, letting the solidified gas evaporate under very low pressure. This time, they found the gas that perches above argon on the Periodic Table: neon.
The most common use of neon is in neon signs, which have a century-long history. First developed by French engineer Georges Claude in 1902, neon lights create light by applying electricity to neon or argon in a sealed glass tube. Argon makes blue light, and neon makes the clear orange-red that is familiar in neon signs, said Bill Concannon, a neon-sign artist and owner of Aargon Neon, a sign shop in Crockett, California.
"It's a great color," Concannon said of neon's orange-red glow. The element's inertness makes it long-lasting as well, he said.
"A well-processed neon tube should be able to run 20 years, continually, without any problem," Concannon, who is also an instructor at the Academy of Art University in San Francisco, told Live Science. Typically, the electrical components of the light fail first, he said.
How a neon sign works
In a neon sign, electrodes on each end of a glass tube filled with neon or argon gas are connected to alternating current. Fifty times a second, the charge on each electrode alternates between positive and negative. Free electrons in the sealed tube have negative charges, so they are drawn to the positively charged electrode. In the process, these electrons crash into the molecules of neon or argon, knocking loose more electrons, Concannon said.
The loss of the electrons leaves the gas molecules positively charged. As the molecules get back to their neutral state, grabbing electrons to do so, they give off light. It's this light that is visible in the glow of a neon sign.
As any trip to Las Vegas or Times Square in New York City will reveal, neon signs aren't only orange and blue, of course. The full palate of colors comes from the glow given off by the gases, the color of the glass and an array of fluorescent powder coatings that can be applied to the glass.
Though electrodes and glass tubes come prefabricated, neon lighting is still a handmade art. Sign creators use blowtorches to heat the glass tubes, bending them and sealing them together in colorful designs before pumping the gas into the tubes and sealing them.
"It's really on a human scale," Concannon said. "No matter how big the design is, the tubes don't weigh that much, and they hardly ever have an overall dimension greater than 8 feet [2.4 meters]."
New LED lights are threatening neon signs' place in public life, Concannon said. Once, for example, most mall signs were lit by neon. Today, stores use LEDs instead. But neon has a throwback "cool" charm that makes it popular as a decoration even for modern tech companies, Concannon said.
"I kind of like being part of that urban landscape at night — even one that I'm hardly ever awake to see," he said.
- The precursor to today's neon lights was invented in 1855, when German physicist Heinrich Geissler began experimenting with sealing gases, such as mercury vapor, in vacuum tubes and exposing them to electricity to create a glow. This was before neon itself had been isolated.
- In liquid form, neon has three times the refrigerating capacity of liquid hydrogen and 40 times that of liquid helium, according to the Royal Society of Chemistry. This chill factor makes neon an important refrigerant in cryogenics, the science of freezing things to very low temperatures. (Neon can also be used for cryonics, the freezing of corpses in hopes that they can be revived by future medical technologies.)
- Neon is the fourth-most abundant element in the universe, but not on Earth. Only 0.0018 percent of Earth's atmosphere is neon gas, according to the Thomas Jefferson National Accelerator Laboratory.
- Like neon signs? Head to the Neon Museum of Las Vegas, with its "Neon Boneyard," an outdoor exhibit of defunct Vegas signs dating back to the 1930s.
- The first neon lamp to go on display lit up in Paris on Dec. 11, 1910, according to Neon Library, a site run by neon artist Skip DeBack. The first neon sign ever sold commercially was bought in 1912 by a Paris barber, according to DeBack.
- Neon is a loner. It doesn't form compounds with other elements or react to any other substance, according to the Royal Society of Chemistry.
Today, neon is used to make helium-neon lasers, which are relatively inexpensive. An electric charge excites the neon, and the neon atoms give off light as they return to their neutral state, similar to the way neon signs work, according to the University of California, Santa Barbara. Mirrors concentrate the light into a laser beam. Early LaserDisc players used helium-neon lasers to read the discs.
Neon is also used as a tool in multiple lines of scientific research. In September 2014, researchers reported that drinking wells in Pennsylvania and Texas had been contaminated with methane as a result of badly sealed wells, rather than by the controversial practice of hydraulic fracturing, commonly dubbed "fracking," in which rock is fractured to release oil and natural gas. In the journal Proceedings of the National Academy of Sciences, the team of geochemists said they attached noble gases, such as neon and argon, to the methane in natural gas to trace the rogue methane because neon and argon don't react and thus move, unchanged, along with the natural gas.
Farther from Earth, neon is also used to probe the mysteries of the sun. In July 2014, an instrument called the Optics-Free Spectrometer (OFS) launched into space. According to NASA, the OFS uses neon to detect photons (particle of light) from the sun. The light hits neon atoms in the instrument, forcing it to eject an electron. The spectrometer then measures these electron emissions in order to determine the features of the light that caused the ejections.
- Read more about Heinrich Geissler and the history of neon.
- See hundreds of images of neon signs and find technical information for making neon signs at the Neon Library.
- Learn more about the properties and uses of neon from the Los Alamos National Laboratory.