1937 neon marquee sign for a theater in Auburn, California, as rebuilt in 2006. The large letters on the tower are illuminated in a timed sequence that repeats, "S", "ST", ..., "STATE", off.

Neon signs are made using electrified, luminous tube lights that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December, 1910 by Georges Claude at the Paris Motor Show.^[1] While they are used worldwide, neon signs were extremely popular in the United States from about 1920–1960. The installations in Times Square were famed, and there were nearly 2000 small shops producing neon signs by 1940.^[2][3] In addition to signage, neon lighting is now used frequently by artists and architects,^[2][4][5] and (in a modified form) in plasma display panels and televisions.^[6][7] The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs.

History[link]

Neon sign

1930s neon sign dealer, Anson Brown Building, Ann Arbor, Michigan

The neon sign is an evolution of the earlier Geissler tube, which is an electrified glass tube containing a "rarefied" gas (the gas pressure in the tube is well below atmospheric pressure). When a voltage is applied to electrodes inserted through the glass, an electrical glow discharge results. Geissler tubes were quite popular in the late 1800s, and the different colors they emitted were characteristics of the gases within. They were, however, unsuitable for general lighting; the pressure of the gas inside typically declined in use. The direct predecessor of neon tube lighting was the Moore tube, which used nitrogen or carbon dioxide as the luminous gas and a patented mechanism for maintaining pressure; Moore tubes were sold for commercial lighting for a number of years in the early 1900s.^[8][9]

The discovery of neon in 1898 included the observation of a brilliant red glow in Geissler tubes.^[10] Immediately following neon's discovery, neon tubes were used as scientific instruments and novelties.^[11] A sign created by Perley G. Nutting and displaying the word "neon" may have been shown at the Louisiana Purchase Exposition of 1904, although this claim has been disputed;^[12] in any event, the scarcity of neon would have precluded the development of a lighting product. However, after 1902, Georges Claude's company in France, Air Liquide, began producing industrial quantities of neon, essentially as a byproduct of their air liquefaction business.^[9] From December 3–18, 1910, Claude demonstrated two 12-metre (39 ft) long bright red neon tubes at the Paris Motor Show.^[1][13] This demonstration lit a peristyle of the Grand Palais (a large exhibition hall).^[14] Claude's associate, Jacques Fonseque, realized the possibilities for a business based on signage and advertising. By 1913 a large sign for the vermouth Cinzano illuminated the night sky in Paris, and by 1919 the entrance to the Paris Opera was adorned with neon tube lighting.^[2] Over the next several years, patents were granted to Claude for two innovations still used today: a "bombardment" technique to remove impurities from the working gas of a sealed sign, and a design for the internal electrodes of the sign that prevented their degradation by sputtering.^[9]

In 1923, Georges Claude and his French company Claude Neon introduced neon gas signs to the United States by selling two to a Packard car dealership in Los Angeles. Earle C. Anthony purchased the two signs reading "Packard" for $1,250 apiece.^[1] Neon lighting quickly became a popular fixture in outdoor advertising. Visible even in daylight, people would stop and stare at the first neon signs for hours, dubbed "liquid fire."^[15]

The next major technological innovation in neon lighting and signs was the development of fluorescent tube coatings. Jacques Risler received a French patent in 1926 for these.^[3] Neon signs that use an argon/mercury gas mixture emit a good deal of ultraviolet light. When this light is absorbed by a fluorescent coating, preferably inside the tube, the coating (called a "phosphor") glows with its own color. While only a few colors were initially available to sign designers, after the Second World War (1939–1945) phosphor materials were researched intensively for use in color televisions. About two dozen colors were available to neon sign designers in the 1960s, and today there are nearly 100 available colors.^[5]

Fabrication[link]

Neon tube signs^{[16][17][18][19]} are produced by the craft of bending glass tubing into shapes. A worker skilled in this craft is known as a glass bender, neon bender or tube bender. The neon tube is made out of 4-5' straight sticks of hollow glass sold by sign suppliers to neon shops worldwide, where they are manually assembled into individual custom designed and fabricated lamps. There are many dozens of colors available, determined by the type of glass tubing and the composition of the gas filling.

Neon sign manufacturing is a cottage industry and an eclectic art, and in most cases, is organized as a small family business. Even today, almost all neon tubes are hand made and labor intensive. The shop equipment used to fabricate signs is itself typically custom assembled from scratch from discrete parts by the craftsmen who will use the equipment.

Tubing in external diameters ranging from about 8–15 mm with a 1 mm wall thickness is most commonly used, although 6mm tubing is now commercially available in colored glass tubes. The tube is heated in sections using several types of burners that are selected according to the amount of glass to be heated for each bend. These burners include ribbon, cannon, or crossfires, as well as a variety of gas torches. Ribbon burners are strips of fire that make the gradual bends while crossfires, when used, make the sharp bends.

The interior of the tubes may be coated with a thin phosphorescent powder coating, affixed to the interior wall of the tube by a binding material. The tube is filled with a purified gas mixture, and the gas ionized by a high voltage applied between the ends of the sealed tube through cold cathodes welded onto the ends. The color of the light emitted by the tube may be just that coming from the gas, or the light from the phosphor layer. Different phosphor-coated tubing sections may be butt welded together using glass working torches to form a single tube of varying colors, for effects such as a sign where each letter displays a different color letter within a single word, such as shown in the sign in the photo above right.

"Neon" is used to denote the general type of lamp, but neon gas is only one of the types of tube gases principally used in commercial application. Pure neon gas is used to produce only about a third of the colors. The greatest number of colors is produced by filling with another inert gas, argon, and a drop of mercury (Hg) which is added to the tube immediately after purification. When the tube is ionized by electrification, the mercury evaporates into mercury vapor, which fills the tube and produces strong ultraviolet light. The ultraviolet light thus produced excites the various phosphor coatings designed to produce different colors. Even though this class of neon tubes use no neon at all, they are still denoted as "neon." Mercury-bearing lamps are a type of cold-cathode fluorescent lamps.

Each type of neon tubing produces two completely different possible colors, one with neon gas and the other with argon/mercury. Some "neon" tubes are made without phosphor coatings for some of the colors. Clear tubing filled with neon gas produces the ubiquitous yellowish orange color with the interior plasma column clearly visible, and is the cheapest and simplest tube to make. Traditional neon glasses in America over 20 years old are lead glass that are easy to soften in gas fires, but recent environmental and health concerns of the workers has prompted manufacturers to seek more environmentally safe special soft glass formulas. One of the vexing problems avoided this way is lead glass' tendency to burn into a black spot emitting lead fumes in a bending flame too rich in the fuel/oxygen mixture. Another traditional line of glasses was colored soda lime glasses coming in a myriad of glass color choices, which produce the highest quality, most hypnotically vibrant and saturated hues. Still more color choices are afforded in either coating, or not coating, these colored glasses with the various available exotic phosphors.

Long lifetime[link]

It is the wide range of colors and the ability to make a tube that can last for years if not decades without replacement, that makes this an art. Since these tubes require so much custom labor, they would have very little economic viability if they did not have such a long lifetime when well processed. The intensity of neon light produced increases slowly as the tube diameter grows smaller, that is, the intensity varies inversely with the square root of the interior diameter of the tubing, and the resistance of the tube increases as the tubing diameter decreases accordingly, because tube ionization is greatest at the center of the tube, and the ions migrate to and are recaptured and neutralized at the tube walls. The greatest cause of neon tube failure is the gradual absorption of neon gas by high voltage ion implantation into the interior glass walls of the tubes which depletes the gas, and eventually causes the tube resistance to rise to a level that it can no longer light at the rated voltage, but this may take 7–10 years.

The actual cause of 80% of neon sign failures is the burnout of the high voltage electrical wires connecting the tubes inside of metal conduits. A very common type of neon sign is made from a formed metal box having a colored translucent face, called "channel lettering". Newer channel letter signs are being replaced by high brightness LEDs.

This long lifetime has created a practical market for neon use for interior architectural cove lighting in a wide variety of uses including homes, where the tube can be bent to any shape, fitted in a small space, and can do so without requiring tube replacement for a decade or more.

Tube bending[link]

A section of the glass is heated until it is malleable; then it is bent into shape and aligned to a pattern containing the graphics or lettering that the final product will ultimately conform to. This is where the real art of neon comes in that takes some artisans from a year up to several years of practice to master. A tube bender corks off the hollow tube before heating and holds a latex rubber blow hose at the other end, through which he gently presses a small amount of air to keep the tube diameter constant as it is bending. The trick of bending is to bend one small section or bend at a time, heating one part of the tubing so that it is soft, without heating some other part of the tube as well, which would make the bend uncontrollable. A bend, once the glass is heated, must be brought to the pattern and fitted rapidly before the glass hardens again because it is difficult to reheat once completely cooled without risking breakage. It is frequently necessary to skip one or more bends and come back to it later, by measuring carefully along the length of the tube. One tube letter may contain 7-10 small bends, and mistakes are not easily corrected without going back and starting all over again. If more tubing is required, another piece is welded onto it, or the parts can be all welded onto each other at the final step. The finished tube must be absolutely vacuum tight to operate, and it must be vacuum clean inside. Once the tube is filled with mercury, if any mistake is made after that, the entire tube had, or should, be started over again, because breathing heated mercury impregnated glass and phosphor causes long term heavy metal poisoning in neon workers. Sticks of tubing are joined until the tube reaches an impractical size, and several tubes are joined in series with the high voltage neon transformer. Extreme ends of the electrical circuit must be isolated from each other to prevent tube puncture and buzzing from corona effect.

Bombardment[link]

A cold cathode electrode is melted (or welded) to each end of the tube as it is finished. The electrodes are also traditionally lead glass and contain a small metal shell with two wires protruding through the glass to which the sign wiring will later be attached. All welds and seals must be perfectly leak-proof to high vacuum before proceeding further.

The tube is attached to a manifold which is itself attached to a high-quality vacuum pump. The tube is then evacuated of air until it reaches near-vacuum. During evacuation, a high current is forced through the tube via the wires protruding from each electrode (in a process known as "bombarding"). This current and voltage is far above the level that occurs in final operation of the tube. The current depends on the specific electrodes used and the diameter of the tube, but is typically in the 450 mA to 800 mA range, at an applied voltage usually between 22,000-26,000 V. The bombarding transformer acts as an adjustable constant current source, and the voltage produced depends on the length and pressure of the tube. Typically the operator will maintain the pressure as high as the bombarder will allow to ensure maximum power dissipation and heating.

This very high power dissipation in the tube heats the glass walls to a temperature of several hundred degrees Celsius, and any dirt and impurities within are drawn off in the gasified form by the vacuum pump. The greatest impurities that are driven off this way are the gases that coat the inside wall of the tubing by adsorption, mainly oxygen, carbon dioxide, and especially water vapor. The current also heats the electrode metal to over 600^oC, producing a bright orange incandescent color. The cathodes are prefabricated hollow metal shells with a small opening (sometimes a ceramic donut aperture) which contains in the interior surface of the shell a light dusting of a cold cathode low work function powder (usually a powder ceramic molar eutectic point mixture including BaCO₂), combined with other alkaline earth oxides, which reduces to BaO₂ when heated to about 500 degrees F, and reduces the work function of the electrode for cathodic emission. Barium Oxide has a work function of roughly 2 whereas tungsten at room temperature has a work function exponentially 100 times more, or 4.0. This represents the cathode drop or electron energy required to remove electrons from the surface of the cathode. This avoids the necessity of using a hot wire thermoelectric cathode such as is used in conventional fluorescent lamps. And for that reason, neon tubes are extremely long lived when properly processed, in contrast to fluorescent tubing, because there is no wire filament as there is in a fluorsecent tube to burn out like a common light bulb. The principal purpose of doing this is to purify the interior of the tube before the tube is sealed off so that when it is operated, these gases and impurities are not driven off and released by the plasma and the heat generated into the sealed tube, which would quickly burn the metal cathodes and mercury droplets (if pumped with argon/mercury) and oxidize the interior gases and cause immediate tube failure. The more thorough the purification of the tube is, the longer lasting and stable the tube will be in actual operation. Once these gases and impurities are liberated under pre-filling bombardment into the tube interior they are quickly evacuated by the pump.

While still attached to the manifold, the tube is allowed to cool while pumping down to the lowest pressure the system can achieve. It is then filled to a low pressure of a few torrs (millimeters of mercury) with one of the noble gases, or a mixture of them, and sometimes a small amount of mercury. This gas fill pressure represents roughly 1/100th of the pressure of the atmosphere. The required pressure depends on the gas used and the diameter of the tube, with optimal values ranging from 6 Torr (0.8 kPa) (for a long 20 mm tube filled with argon/mercury) to 27 Torr (3.6 kPa) (for a short 8 mm diameter tube filled with pure neon). Neon or argon are the most common gases used; krypton, xenon, and helium are used by artists for special purposes but are not used alone in normal signs. A premixed combination of argon and helium is often used in lieu of pure argon when a tube is to be installed in a cold climate, since the helium increases voltage drop (and thus power dissipation), warming the tube to operating temperature faster. Neon glows bright red or reddish orange when lit. When argon or argon/helium is used, a tiny droplet of mercury is added. Argon by itself is very dim pale lavender when lit, but the droplet of mercury fills the tube with mercury vapor when sealed, which then emits ultraviolet light upon electrification. This ultraviolet emission allows finished argon/mercury tubes to glow with a variety of bright colors when the tube has been coated on the interior with ultraviolet-sensitive phosphors after being bent into shape.

Heat processed neon tubes[link]

An alternate way of processing finished neon tubes has also been used. Because the only purpose of bombardment by electrical means is to purify the interior of tubes, it is also possible to produce a tube by heating the tube externally either with a torch or with an oven, while heating the electrode with a Radio Frequency Induction Heating coil (RFIH). While this is less productive, it creates a cleaner custom tube with significantly less cathode damage, longer life and brilliance, and can produce tubes of very small sizes and diameters, down to 6mm OD. The tube is heated thoroughly under high vacuum without external electrical application, until the outgassed gases can be seen to have been totally depleted and the pressure drops to a high vacuum again. Then the tube is filled, sealed and the mercury dropped and shaken.

Electrical wiring[link]

The finished glass pieces are illuminated by either a neon sign transformer or a switched-mode power supply running at voltages ranging between 3-15 kV and currents between 20 and 120 mA. These power supplies operate as constant-current sources (a high voltage supply with a very high internal impedance), since the tube has a negative characteristic electrical impedance. Standard tube tables established in the early days of neon are still used that specify the gas fill pressures, in either Ne or Hg/Ar, as a function of tube length in feet, tube diameter and transformer voltage.

The standard traditional neon transformer, a magnetic shunt transformer, is a special non-linear type designed to keep the voltage across the tube raised to whatever level is necessary to produce the fixed current needed. The voltage drop of a tube is proportional to length and so the maximum voltage and length of tubing fed from a given transformer is limited.

Compact high frequency inverter-converter transformers developed in the early 1990s are used, especially when low Radio Frequency Interference (RFI) is needed, such as in locations near high-fidelity sound equipment. At the typical frequency of these solid state transformers, the plasma electron-ion recombination time is too long to extinguish and reignite the plasma at each cycle, unlike the case at power line frequency. The plasma does not broadcast high frequency switching noise and remains ionized continually, becoming radio noise free.^{[citation needed]}

The most common current rating is 30 mA for general use, with 60 mA used for high-brightness applications like channel letters or architectural lighting. 120 mA sources are occasionally seen in illuminating applications, but are uncommon since special electrodes are required to withstand the current, and an accidental shock from a 120 mA transformer is much more likely to be fatal than from the lower current supplies.

The efficiency of neon lighting ranges between that of ordinary incandescent lights and that of fluorescent lamps, depending on color. On a per-watt basis, incandescents produce 10 to 20 lumens, while fluorescents produce 50 to 100 lumens. Neon light efficiency ranges from 10 lumens per watt for red, up to 60 lumens for green and blue when these colors result from internal phosphor coatings.^[20]

Blocking out and coating[link]

Club Prima Donna animated neon sign in Reno, Nevada, 1955.

A trick of the eye is used to produce visually distinct neon display segments by blocking out parts of the tube with an opaque coating. One complete assembly may be composed of contiguous tube elements joined by glass welding to one another so that the same current passes through, for example, several letters joined end to end from cathode to cathode. To the untrained eye, this looks like separate tubes, but the electrical splice is the plasma inside the crossover glass itself. The entire tube lights up, but the segments that the viewer is not supposed to see are covered with highly opaque special black or gray glass paint. This heat-resistant coating is either painted on or dipped. Without blockout paint, the unintended visual connections would make the display appear confusing.

In most mass produced low-priced signs today, clear glass tubing is coated with translucent paint to produce colored light. In this way, several different colors can be produced inexpensively from a single glowing tube. Over time, elevated temperatures, thermal cycling, or exposure to weather may cause the colored coating to flake off the glass or change its hue. A more expensive alternative is to use high-quality colored glass tubing, which retains a more stable appearance as it ages.

Applications[link]

Light-emitting tubes form colored lines with which a text can be written or a picture drawn, including various decorations, especially in advertising and commercial signage. By programming sequences of switching parts on and off, there are many possibilities for dynamic light patterns that form animated images.

In some applications, neon tubes are increasingly being replaced with LEDs, given the steady advance in LED luminosity and decreasing cost of high-intensity LEDs.^[21] However, proponents of neon technology maintain that they still have significant advantages over LEDs.^[22]

Images of neon signs[link]

• 

  Helium

• 

  Neon

• 

  Argon (with Mercury)

• 

  Krypton

• 

  Xenon

• 

  A deteriorated, 1950s era sign typical of Googie architecture; "Ships" was a chain of coffee shops in Los Angeles.^[23]

• 

  Original Whitey's Restaurant "EAT" sign in Arlington, VA

See also[link]

• Neon lighting
• Gas discharge lamp
• Crackle tube
• Plasma globe
• Neon message board
• Westinghouse Sign
• Timeline of lighting technology

References[link]

Further reading[link]

• "2010 Top Ten Endangered Sites". Heritage Vancouver Society. http://www.heritagevancouver.org/topten/2010/topten2010_09.html. Retrieved 2010-12-05. 
• Bass, Shermakaye (2007-06-06). "Neon Museum saving Las Vegas' iconic signs". Los Angeles Times. http://travel.latimes.com/articles/la-trw-neonvegas10jun10. Retrieved 2009-09-12. 
• Crowley, David (September 2007). "Life in the Darkness". Creative Review. http://polishneon.com/pages/history.html. Retrieved 2010-12-26.  Article about neon signage's flowering and decline in Warsaw and Poland.
• Keen, Judy (October 6, 2008). "Save neon signs, fans urge". USA Today. http://www.usatoday.com/news/nation/2008-10-06-neon-signs_N.htm. 

External links[link]

Wikibooks has a book on the topic of Making Neon Signs

Wikimedia Commons has media related to: Neon signs

• Johansson, Feddy. "Svenska Neonskyltar". http://www.svenskaneonskyltar.se.  Collection of photographs of Swedish neon signs; text in Swedish.
• "Neon Muzeum". NeonMuzeum.com. http://polishneon.com/pages/index_uk.html.  Website of an organization devoted to preserving Polish neon signs; in English.

fluorine ← neon → sodium He ↑ Ne ↓ Ar 10Ne Periodic table
Appearance
Colorless gas exhibiting an orange-red glow when placed in a high voltage electric field Neon gas in a discharge tube, so-called neon light. Spectral lines of neon in the visible region
General properties
Name, symbol, number	neon, Ne, 10
Pronunciation	/ˈniːɒn/
Element category	noble gases
Group, period, block	18, 2, p
Standard atomic weight	20.1797(6)
Electron configuration	1s2 2s2 2p6
Electrons per shell	2, 8 (Image)
Physical properties
Phase	gas
Density	(0 °C, 101.325 kPa) 0.9002 g/L
Liquid density at b.p.	1.207[1] g·cm−3
Melting point	24.56 K, -248.59 °C, -415.46 °F
Boiling point	27.07 K, -246.08 °C, -410.94 °F
Triple point	24.5561 K (-249°C), 43[2][3] kPa
Critical point	44.4 K, 2.76 MPa
Heat of fusion	0.335 kJ·mol−1
Heat of vaporization	1.71 kJ·mol−1
Molar heat capacity	5R/2 = 20.786 J·mol−1·K−1
Vapor pressure
P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 12 13 15 18 21 27
Atomic properties
Oxidation states	no data
Ionization energies (more)	1st: 2080.7 kJ·mol−1
	2nd: 3952.3 kJ·mol−1
	3rd: 6122 kJ·mol−1
Covalent radius	58 pm
Van der Waals radius	154 pm
Miscellanea
Crystal structure	face-centered cubic
Magnetic ordering	diamagnetic[4]
Thermal conductivity	49.1x10-3  W·m−1·K−1
Speed of sound	(gas, 0 °C) 435 m·s−1
Bulk modulus	654 GPa
CAS registry number	7440-01-9
Most stable isotopes
Main article: Isotopes of neon
iso NA half-life DM DE (MeV) DP 20Ne 90.48% 20Ne is stable with 10 neutrons 21Ne 0.27% 21Ne is stable with 11 neutrons 22Ne 9.25% 22Ne is stable with 12 neutrons
v t e · r

Neon ( /ˈniːɒn/ NEE-on) is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or in high-voltage discharge tubes or neon advertising signs.^[5][6] It is commercially extracted from air, in which it is found in trace amounts.

History[link]

Neon gas-discharge lamps forming the symbol for Neon "Ne".

Neon (Greek νέον (neon) meaning "new one") was discovered in 1898 by the British chemists Sir William Ramsay (1852–1916) and Morris W. Travers (1872–1961) in London.^[7] Neon was discovered when Ramsay chilled a sample of air until it became a liquid, then warmed the liquid and captured the gases as they boiled off. The gases that boiled off, in addition to nitrogen, oxygen, and argon, were krypton, xenon, and neon.^[8] The characteristic, brilliant red color that is emitted by gaseous neon when excited electrically was noted immediately; Travers later wrote, "the blaze of crimson light from the tube told its own story and was a sight to dwell upon and never forget."^[9]

Neon's scarcity precluded its prompt application for lighting along the lines of Moore tubes, which used nitrogen and which were commercialized in the early 1900s. After 1902, Georges Claude's company, Air Liquide, was producing industrial quantities of neon as a byproduct of his air liquefaction business, and in December 1910 Claude demonstrated modern neon lighting based on a sealed tube of neon. In 1912, Claude's associate began selling neon discharge tubes as advertising signs. They were introduced to U.S. in 1923, when two large neon signs were bought by a Los Angeles Packard car dealership. The glow and arresting red color made neon advertising completely different from the competition.^[10]

Neon played a role in the basic understanding of the nature of atoms in 1913, when J. J. Thomson, as part of his exploration into the composition of canal rays, channeled streams of neon ions through a magnetic and an electric field and measured their deflection by placing a photographic plate in their path. Thomson observed two separate patches of light on the photographic plate (see image), which suggested two different parabolas of deflection. Thomson eventually concluded that some of the atoms in the neon gas were of higher mass than the rest. Though not understood at the time by Thomson, this was the first discovery of isotopes of stable atoms. It was made by using a crude version of an instrument we now term as a mass spectrometer.

Creation[link]

Stable forms of neon are produced in stars. It is created in fusing helium and oxygen in the alpha process, which requires temperatures above 100 megakelvins and masses greater than 3 solar masses.

Isotopes[link]

The first evidence for isotopes of a stable element. In the bottom right corner of J. J. Thomson's photographic plate are the separate impact marks for the two isotopes neon-20 and neon-22.

Neon is the second lightest inert gas. Neon has three stable isotopes: ²⁰Ne (90.48%), ²¹Ne (0.27%) and ²²Ne (9.25%). ²¹Ne and ²²Ne are partly primordial and partly nucleogenic (i.e., made by nuclear reactions of other nuclides with neutrons or other particles in the environment) and their variations in natural abundance are well understood. In contrast, ²⁰Ne (the chief primordial isotope made in stellar nucleosynthesis) is not known to be nucleogenic or radiogenic (save for cluster decay production, which is thought to produce only a small amount). The causes of the variation of ²⁰Ne in the Earth have thus been hotly debated.^[11]

The principal nuclear reactions which generate nucleogenic neon isotopes start from ²⁴Mg and ²⁵Mg, which produce ²¹Ne and ²²Ne, respectively, after neutron capture and immediate emission of an alpha particle. The neutrons that produce the reactions are mostly produced by secondary spallation reactions from alpha particles, in turn derived from uranium-series decay chains. The net result yields a trend towards lower ²⁰Ne/²²Ne and higher ²¹Ne/²²Ne ratios observed in uranium-rich rocks such as granites.^[12] Neon-21 may also be produced in a nucleogenic reaction, when ²⁰Ne absorbs a neutron from various natural terrestrial neutron sources.

In addition, isotopic analysis of exposed terrestrial rocks has demonstrated the cosmogenic (cosmic ray) production of ²¹Ne. This isotope is generated by spallation reactions on magnesium, sodium, silicon, and aluminium. By analyzing all three isotopes, the cosmogenic component can be resolved from magmatic neon and nucleogenic neon. This suggests that neon will be a useful tool in determining cosmic exposure ages of surface rocks and meteorites.^[13]

Similar to xenon, neon content observed in samples of volcanic gases is enriched in ²⁰Ne, as well as nucleogenic ²¹Ne, relative to ²²Ne content. The neon isotopic content of these mantle-derived samples represents a non-atmospheric source of neon. The ²⁰Ne-enriched components are attributed to exotic primordial rare gas components in the Earth, possibly representing solar neon. Elevated ²⁰Ne abundances are found in diamonds, further suggesting a solar neon reservoir in the Earth.^[14]

Characteristics[link]

Neon discharge tube

Neon is the second-lightest noble gas, after helium. It glows reddish-orange in a vacuum discharge tube. Also, neon has the narrowest liquid range of any element: from 24.55 K to 27.05 K (−248.45 °C to −245.95 °C, or −415.21 °F to −410.71 °F). It has over 40 times the refrigerating capacity of liquid helium and three times that of liquid hydrogen (on a per unit volume basis).^[1] In most applications it is a less expensive refrigerant than helium.^[15]

Spectrum of neon with ultraviolet (at left) and infrared (at right) lines shown in white

Neon plasma has the most intense light discharge at normal voltages and currents of all the noble gases. The average color of this light to the human eye is red-orange due to many lines in this range; it also contains a strong green line which is hidden, unless the visual components are dispersed by a spectroscope.^[16]

Two quite different kinds of neon lighting are in common use. Neon glow lamps are generally tiny, with most operating at about 100–250 volts.^[17] They have been widely used as power-on indicators and in circuit-testing equipment, but light-emitting diodes (LEDs) now dominate in such applications. These simple neon devices were the forerunners of plasma displays and plasma television screens.^[18][19] Neon signs typically operate at much higher voltages (2–15 kilovolts), and the luminous tubes are commonly meters long.^[20] The glass tubing is often formed into shapes and letters for signage as well as architectural and artistic applications.

Occurrence[link]

Neon is actually abundant on a universal scale; it is the fifth most abundant chemical element in the universe by mass, after hydrogen, helium, oxygen, and carbon (see chemical element). Its relative rarity on Earth, like that of helium, is due to its relative lightness, high vapor pressure at very low temperatures, and chemical inertness, all properties which tend to keep it from being trapped in the condensing gas and dust clouds which resulted in the formation of smaller and warmer solid planets like Earth.

Neon is monatomic, making it lighter than the molecules of diatomic nitrogen and oxygen which form the bulk of Earth's atmosphere; a balloon filled with neon will rise in air, albeit more slowly than a helium balloon.^[21]

Mass abundance in the universe is about 1 part in 750 and in the Sun and presumably in the proto-solar system nebula, about 1 part in 600. The Galileo spacecraft atmospheric entry probe found that even in the upper atmosphere of Jupiter, the abundance of neon is reduced (depleted) by about a factor of 10, to a level of 1 part in 6,000 by mass. This may indicate that even the ice-planetesimals which brought neon into Jupiter from the outer solar system, formed in a region which was too warm for them to have kept their neon (abundances of heavier inert gases on Jupiter are several times that found in the Sun).^[22]

Neon is rare on Earth, found in the Earth's atmosphere at 1 part in 65,000 (by volume) or 1 part in 83,000 by mass. It is industrially produced by cryogenic fractional distillation of liquefied air.^[1]

Applications[link]

"Neon" signs may use neon along with other noble gases.

Neon is often used in signs and produces an unmistakable bright reddish-orange light. Although still referred to as "neon", all other colors are generated with the other noble gases or by many colors of fluorescent lighting.

Neon is used in vacuum tubes, high-voltage indicators, lightning arrestors, wave meter tubes, television tubes, and helium-neon lasers. Liquefied neon is commercially used as a cryogenic refrigerant in applications not requiring the lower temperature range attainable with more extreme liquid helium refrigeration.

Both neon gas and liquid neon are relatively expensive – for small quantities, the price of liquid neon can be more than 55 times that of liquid helium. The driver for neon's expense is the rarity of neon, which unlike helium, can only be obtained from air.

The triple point temperature of neon (24.5561 K) is a defining fixed point in the International Temperature Scale of 1990.^[2]

Compounds[link]

Neon is the first p-block noble gas. Neon is generally considered to be inert. No true neutral compounds of neon are known. However, the ions Ne⁺, (NeAr)⁺, (NeH)⁺, and (HeNe⁺) have been observed from optical and mass spectrometric studies, and there are some unverified reports of an unstable hydrate.^[1]

See also[link]

• Expansion ratio
• Neon sign
• Neon lamp

Books View or order collections of articles	Neon Period 2 elements Noble gases Chemical elements (sorted alphabetically) Chemical elements (sorted by number)
Portals Access related topics	Chemistry portal
Find out more on Wikipedia's Sister projects	Images and media from Commons Definitions from Wiktionary Textbooks from Wikibooks Learning resources from Wikiversity

References[link]

External links[link]

• The Periodic Table of Videos video of Neon at YouTube
• WebElements.com – Neon.
• It's Elemental – Neon
• USGS Periodic Table – Neon
• Atomic Spectrum of Neon
• Neon Museum, Las Vegas

vep:Neon

This article does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (March 2008)

This biohazard sign is a completely conventional symbol with no inherent relationship to what it represents.

A sign is a representation of an object that implies a connection between itself and its object. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence. (This is in contrast to a symbol which stands for another thing, as a flag may be a symbol of a nation).

Door sign

The way a sign signifies is called semiosis which is a topic of semiotics and philosophy of language.

How a sign is perceived depends upon what is intended or expressed in the semiotic relationship of:

• Signification
• Significance (i.e. meaning)
• Importance

Thus, for example, people may speak of the significance of events, the signification of characters, the meaning of sentences, or the import of a communication. Different ways of relating signs to their objects are called modes of signification.

Uses of conventional signs are varied. Usually the goal is to elicit a response or simply inform. That can be achieved by marking something, displaying a message (i.e. a notice), drawing attention or presenting evidence of an underlying cause (for instance, medical symptoms signify a disease), performing a bodily gesture, etc.

Nature[link]

Semiotics, epistemology, logic, and philosophy of language are concerned about the nature of signs, what they are and how they signify. The nature of signs and symbols and significations, their definition, elements, and types, is mainly established by Aristotle, Augustine, and Aquinas. According to these classic sources, significance is a relationship between two sorts of things: signs and the kinds of things they signify (intend, express or mean), where one term necessarily causes something else to come to the mind. Distinguishing natural signs and conventional signs, the traditional theory of signs^[who?] sets the following threefold partition of things:

1. There are things that are just things, not any sign at all;
2. There are things that are also signs of other things (as natural signs of the physical world and mental signs of the mind);
3. There are things that are always signs, as languages (natural and artificial) and other cultural nonverbal symbols, as documents, money, ceremonies, and rites.

Pedestrian crossing sign

Thus there are things which may act as signs without any respect to the human agent (the things of the external world, all sorts of indications, evidences, symptoms, and physical signals), there are signs which are always signs (the entities of the mind as ideas and images, thoughts and feelings, constructs and intentions); and there are signs that have to get their signification (as linguistic entities and cultural symbols). So, while natural signs serve as the source of signification, the human mind is the agency through which signs signify naturally occurring things, such as objects, states, qualities, quantities, events, processes, or relationships. Human language and discourse, communication, philosophy, science, logic, mathematics, poetry, theology, and religion are only some of fields of human study and activity where grasping the nature of signs and symbols and patterns of signification may have a decisive value.

Types[link]

A sign can denote any of the following:

The western zodiac signs

A signboard on a beach in Durban in apartheid-era South Africa indicates a racially segregated beach.

• Sign, in astrology: often used to mean the Sun sign
• Sign or signing, in communication: communicating via hand gestures, such as in sign language.
• Gang signal
• Sign, in Tracking (hunting): also known as Spoor (animal); trace evidence left on the ground after passage.
• A signboard.
• A sign, in common use, is an indication that a previously observed event is about to occur again
• Sign, in divination and religion: an omen, an event or occurrence believed to foretell the future
• Sign, in ontology and spirituality: a coincidence; see synchronicity
• Sign (linguistics): a combination of a concept and a sound-image described by Ferdinand de Saussure
• In mathematics, the sign of a number tells whether it is positive or negative. Also, the sign of a permutation tells whether it is the product of an even or odd number of transpositions.
• Signedness, in computing, is the property that a representation of a number has one bit, the sign bit, which denotes whether the number is non-negative or negative. A number is called signed if it contains a sign bit, otherwise unsigned. See also signed number representation
• Sign, in biology: an indication of some living thing's presence
• Medical sign, in medicine: objective evidence of the presence of a disease or disorder, as opposed to a symptom, which is subjective
• Sign (semiotics): the basic unit of meaning
• Information sign: a notice that instructs, advises, informs or warns people
• Traffic sign: a sign that instructs drivers; see also stop sign, speed limit sign, cross walk sign
• Sign, in a writing system: a basic unit. Similar terms which are more specific are character, letter or grapheme
• Commercial signage, including flashing signs, such as on a retail store, factory, or theatre
• Signature, in history: a handwritten depiction observed on a document to show authorship and will

See also[link]

References[link]

Look up sign in Wiktionary, the free dictionary.

Jonathan Richman
Live at the Blind Pig, Ann Arbor, Michigan (2005)
Background information
Born	(1951-05-16) May 16, 1951 (age 61) Natick, Massachusetts, United States
Genres	Rock, New wave, proto-punk, singer-songwriter
Occupations	Musician, songwriter
Instruments	Guitarist, vocalist, saxophonist
Years active	1970 – present
Labels	Beserkley Records
Associated acts	The Modern Lovers

Jonathan Michael Richman^[1] (born May 16, 1951)^[2] is an American singer, songwriter and guitarist. In 1970 he founded The Modern Lovers, an influential proto-punk band. Since the mid-1970s, Richman has worked either solo or with low-key, generally acoustic backing. He is known for his wide-eyed,^[3] unaffected and child-like outlook, and music that, while rooted in rock and roll, often draws on influences from around the world.

Biography[link]

Early life[link]