Information AboutHelium |
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Helium (from ; its atomic symbol is '''He'''. It is a colorless, odorless, tasteless, non-toxic, and nearly inert monatomic that heads the Noble Gas series in the Periodic Table . Its Atomic Number is 2 and its Boiling and Melting points are the lowest among the elements. It exists only as a Gas except in extreme conditions. Extreme conditions are also needed to create the small handful of helium Compound s, which are all unstable at Standard Temperature And Pressure . Its most abundant Stable Isotope is Helium-4 and it has a rare stable Isotope , Helium-3 . The behavior of Liquid Helium -4's two different states—helium I and helium II—is important to researchers studying Quantum Mechanics (in particular the phenomenon of Superfluidity ) and those looking at the effects that near Absolute Zero temperatures have on Matter (such as Superconductivity ). Helium is the second most Abundant element in the known Universe and second lightest element in the Periodic Table . In the modern Universe almost all new helium is created as a result of the Nuclear Fusion of Hydrogen in Star s. On Earth it is created by the Radioactive Decay of much heavier elements ( Alpha Particle s are helium-4 nuclei produced by Alpha-decay ). After its creation, part of it is trapped with Natural Gas in concentrations up to 7% by volume. It is extracted from the natural gas by a low Temperature separation process called Fractional Distillation . In 1868 the French astronomer ἥλιος which is, surprisingly, Cognate with the English ''sun''.) Helium is used in Cryogenics , in deep-sea breathing systems, to cool Superconducting Magnet s, in Helium Dating , for inflating Balloon s, for providing lift in Airship s and as a protective gas for many industrial uses (such as Arc Welding and growing Silicon wafers). Inhaling a small Volume of the gas temporarily changes the quality of one's voice. However, inhaling it from a typical commercial source, such as that used to fill balloons, can be dangerous due to the number of contaminants that may be present. These could include trace amount of other gases, in addition to aerosolized lubricating oil. Notable characteristics Gas and plasma phases Helium is a colorless, odorless, and non-toxic gas. It is the least reactive member of group 18 (the is closer to unity than any other gas. This gas has a negative Joule-Thomson Coefficient at normal ambient temperatures, meaning it heats up when allowed to freely expand. Only below its Joule-Thomson Inversion Temperature (of about 40 K at 1 atmosphere) does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling. Helium is chemically unreactive under all normal conditions due to its Valence of zero. It is an electrical insulator unless Ion ized. As with the other noble gases, helium has metastable Energy Level s that allow it to remain ionized in an Electrical discharge with a Voltage below its Ionization Potential . Helium can form unstable Compound s with Tungsten , Iodine , Fluorine , Sulfur and Phosphorus when it is subjected to an Electric Glow Discharge , through electron bombardment or is otherwise a Plasma . HeNe, HgHe10, WHe2 and the molecular ions He2+, He2++, HeH+, and HeD+ have been created this way. This technique has also allowed the production of the neutral molecule He2, which has a large number of Band System s, and HgHe, which is apparently only held together by polarization forces . Theoretically, other compounds, like helium fluorohydride (HHeF), may also be possible. Throughout the Universe, helium is found mostly in a Plasma state whose properties are quite different to molecular helium. As a plasma, helium's electrons and protons are not bound together, resulting in very high electrical conductivity, even when the gas is only partially ionized. The charged particles are highly influenced by magnetic and electric fields. For example, in the Solar Wind together with ionized hydrogen, they interact with the Earth's Magnetosphere giving rise to Birkeland Current s and the Aurora . Solid and liquid phases Helium solidifies only under great pressure. The resulting colorless, almost invisible of the two phases are nearly the same. The solid has a sharp Melting Point and has a Crystal line structure. Helium I state Below its Boiling Point of 4.21 Kelvin s and above the Lambda Point of 2.1768 kelvins, the Isotope helium-4 exists in a normal colorless Liquid state, called ''helium I''. Like other cryogenic liquids, helium I boils when heat is added to it. It also contracts when its temperature is lowered until it reaches the Lambda Point , when it stops boiling and suddenly expands. The rate of expansion decreases below the lambda point until about 1 K is reached; at which point expansion completely stops and helium I starts to contract again. Helium I has a gas-like is needed to explain this property and thus both types of liquid helium are called ''quantum fluids'', meaning they display atomic properties on a macroscopic scale. This is probably due to its boiling point being so close to absolute zero, which prevents random molecular motion ( Heat ) from masking the atomic properties. Helium II state Liquid helium below its lambda point begins to exhibit very unusual characteristics, in a state called ''helium II''. Boiling of helium II is not possible due to its high Thermal Conductivity ; heat input instead causes Evaporation of the liquid directly to gas. The isotope helium-3 also has a superfluid phase, but only at much lower temperatures; as a result, less is known about such properties in the isotope helium-3. also covers the interior of the larger container; if it were not sealed, the helium II would creep out and escape.]] Helium II is a Superfluid , a quantum-mechanical state of matter with strange properties. For example, when it flows through even capillaries of 10-7 to 10-8 m width it has no measurable Viscosity . However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium was observed. Current theory explains this using the ''two-fluid model'' for Helium II. In this model, liquid helium below the lambda point is viewed as containing a proportion of helium atoms in a Ground State , which are superfluid and flow with exactly zero viscosity, and a proportion of helium atoms in an excited state, which behave more like an ordinary fluid. Helium II also exhibits a "creeping" effect. When a surface extends past the level of helium II, the helium II moves along the surface, seemingly against the force of Gravity . Helium II will escape from a vessel that is not sealed by creeping along the sides until it reaches a warmer region where it evaporates. It moves in a 30 Nm thick film regardless of surface material. This film is called a Rollin Film and is named after the man who first characterized this trait, B. V. Rollin . As a result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine liquid helium. Unless the container is carefully constructed, the helium II will creep along the surfaces and through valves until it reaches somewhere warmer, where it will evaporate. In the ''fountain effect'', a chamber is constructed which is connected to a reservoir of helium II by a Sintered disc through which superfluid helium leaks easily but through which non-superfluid helium cannot pass. If the interior of the container is heated, the superfluid helium changes to non-superfluid helium. In order to maintain the equilibrium fraction of superfluid helium, superfluid helium leaks through and increases the pressure, causing liquid to fountain out of the container. The thermal conductivity of helium II is greater than that of any other known substance, a million times that of helium I and several hundred times that of Copper . This is because heat conduction occurs by an exceptional quantum-mechanical mechanism. Most materials that conduct heat well have a Valence Band of free electrons which serve to transfer the heat. Helium II has no such valence band but nevertheless conducts heat well. The Flow Of Heat is governed by Equation s that are similar to the Wave Equation used to characterize Sound propagation in air. So when heat is introduced, it will move at 20 meters per second at 1.8 K through helium II as waves in a phenomenon called ''second sound''. Electron energy levels Depending on the spin orientation of the two electrons in the helium atom, one speaks of Parahelium for two anti-parallel spins (S=0) and of Orthohelium for two parallel spins (S=1). For the orthohelium one of the electrons does not sit in the ground orbital (1s). {Link without Title} Applications s such as the USGS blimp.]] Pressurized helium is commercially available. Helium is used for many purposes that require one or more of its unique properties; low Boiling Point , low Density , low Solubility , high Thermal Conductivity , or its Inert ness. Airship s and Balloon s ( Toy , Weather , and Research ) are inflated with helium because it is Lighter Than Air (1 m³ of helium will lift 1 kg). Helium is currently preferred to Hydrogen in airships because, while it is more expensive, it is not flammable and has 92.64% of the lifting power of hydrogen. '' Heliox '', a mixture of helium and Oxygen , is used in commercial deep-sea Breathing Gas systems to reduce the risk of Nitrogen Narcosis (high pressure Nitrogen having a Narcotic effect on the Brain ) and Oxygen Toxicity at high pressures. Higher pressures require a greater proportion of helium and reduced amounts of nitrogen and oxygen (every ten-meter increase in depth yields a one atmosphere increase of pressure). '' Trimix '', a mixture of oxygen, nitrogen and helium, and Heliair , a mixture of Air and helium, is also used in this way. Trimix is fast becoming the standard for technical diving deeper than 40 meters, and Heliox is now rarely used for non-commercial diving, due to the risk of High Pressure Nervous Syndrome . Below 130 meters (430 ft) a mixture of hydrogen, helium, and oxygen called '' Hydreliox '' is sometimes used to help prevent High Pressure Nervous Syndrome , but is quite rare, due to the explosive nature of hydrogen. All these uses rely on helium's very low solubility in water (the major component of blood). The extremely low Boiling Point makes helium useful as a coolant in Magnetic Resonance Imaging , Superconducting Magnet s, Cryogenics , and to remove thermal noise from detectors used in Astronomy . The extreme coldness of liquid helium is also used to produce Superconductivity in some ordinary Metal s such as Lead (lead becomes superconductive at 7.3 K), allowing for a completely free flow of electrons in the metal. Other uses:
History Discoveries Helium was named the element after the Greek word for the Sun god, '' Helios '', and, assuming it was a Metal , gave it an -ium ending (a mistake that was never corrected). British chemist . It was independently isolated from cleveite the same year by Swedish chemists Per Teodor Cleve and Abraham Langlet in Uppsala in Sweden . They collected enough of the gas to accurately determine its Atomic Weight . An and Thomas Royds demonstrated that an Alpha Particle is a helium Nucleus . Helium was first liquefied by Dutch physicist who subjected helium to a similar amount of cooling as Kamerlingh Onnes but at 25 standard atmospheres of pressure. In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that liquid helium-4 has almost no Viscosity at temperatures near Absolute Zero , a phenomenon now called Superfluid ity. In 1972, the same phenomenon was observed in liquid helium-3 by American physicists Douglas D. Osheroff , David M. Lee , and Robert C. Richardson . Production and use Great quantities of helium were found in the natural gas fields of the American , the U.S. Navy's C-7 , which flew its maiden voyage from Hampton Roads, Virginia to Bolling Field in Washington, D.C. on December 7 , 1921 . Although the extraction process, using low-temperature gas liquefaction, was not developed in time to be significant during World War I, production continued. Helium was primarily used as a lifting gas in lighter-than-air craft. This use increased demand during World War II, as well as demands for shielded arc Welding . Helium was also vital in the atomic bomb Manhattan Project . The Government Of The United States set up the National Helium Reserve in 1925 at Amarillo, Texas with the goal of supplying military Airship s in time of War and commercial airships in peacetime. Helium use following World War II was depressed but the reserve was expanded in the 1950s to ensure a supply liquid helium as a coolant to create oxygen/hydrogen Rocket Fuel (among other uses) during the Space Race and Cold War . Helium use in the United States in 1965 was more than eight times the peak wartime consumption. After the "Helium Acts Amendments of 1960" (Public Law 86-777), the U.S. Bureau Of Mines arranged for five private plants to recover helium from natural gas. For this ''helium conservation'' program, the Bureau built a 425-mile pipeline from Bushton, Kansas to connect those plants with the government's Cliffside partially depleted gasfield, near Amarillo, Texas . This helium-nitrogen mixture was injected and stored in the Cliffside Gas Field until needed, when it then was further purified. By 1995 32 billion ft³ (910,000,000 m³) of the gas had been collected and the reserve was US$1.4 billion in debt, prompting the to start liquidating the reserve by 2005. Helium produced before 1945 was about 98% pure (2% Nitrogen ), which was adequate for airships. In 1945 a small amount of 99.9% helium was produced for welding use. By 1949 commercial quantities of Grade A 99.995% helium were available. For many years the United States produced over 90% of commercially usable helium in the world. Extraction plants created in Canada , Poland , Russia , and other nations produced the remaining helium. In the early 2000s, Algeria and Qatar were added as well. Algeria quickly became the second leading producer of helium (16% of total in 2002). Through this time helium consumption has increased, as well as costs. Occurrence and production Abundance Helium is the second most abundant element in the known s, where it is formed from hydrogen by the Nuclear Fusion of the Proton-proton Chain Reaction and CNO Cycle . This so-called 'hydrogen burning' process provides the energy stars need to shine. According to the Big Bang model of the early development of the Universe, the vast majority of helium was formed in the first three minutes after the Big Bang. Its widespread abundance is seen as part of the evidence that supports this Theory . However, in the where it is found in 8 parts per billion (109). Helium only makes up 4 parts per trillion (1012) in Seawater . Essentially all helium on Earth is a result of is found in minerals of Uranium and Thorium , including Cleveite s, Pitchblende , Carnotite , Monazite and Beryl . There are also small amounts in mineral Springs , Volcanic gas and meteoric Iron . Production Helium in the crust is produced by the radioactive decay of s of Texas , Oklahoma , Arizona and Kansas . Helium is also produced in Canada , Poland , the People's Republic Of China , and Qatar . Since helium has a lower boiling point than any other element, low temperature and high pressure are used to liquefy nearly all the other gases (mostly . Diffusion of crude natural gas through special semi- Permeable membranes and other barriers is another method to recover and/or purify helium. Helium can also be synthesized by bombardment of Lithium -6 or Boron with high-velocity Neutron s in a Nuclear Reactor to produce He-4 and Tritium . The tritium decays with a Half Life of 12.5 years to produce He-3. This method of production, however, is not economically viable—at least for making normal commercial-grade helium. Fusion in exploding Hydrogen Bomb s creates helium as well. Isotopes Although there are eight known to study the origin of such rocks. The most common isotope, helium-4, is produced on Earth by Alpha Decay of heavier radioactive elements; the Alpha Particle s that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its Nucleon s are arranged into Complete Shells . It was also formed in enormous quantities during Big Bang Nucleosynthesis , and its abundance serves as a test of cosmological models. Equal mixtures of liquid helium-3 and helium-4 below 0.8 K will separate into two immiscible phases due to their dissimilarity (they follow different s, however, helium-3 is more abundant, a product of Nuclear Fusion . Extraplanetary material, such as Lunar and Asteroid Regolith , have trace amounts of helium-3 from being bombarded by Solar Wind s. The different formation processes of the two stable isotopes of helium produce the differing isotope abundances. These differing isotope abundances can be used to investigate the origin of rocks and the composition of the Earth's Mantle . It is possible to produce Exotic Helium Isotopes , which rapidly decay into other substances. The shortest-lived isotope is helium-5 with a Half-life of 7.6×10−22 second. Helium-6 decays by emitting a Beta Particle and has a half life of 0.8 second. Helium-7 also emits a beta particle as well as a Gamma Ray . Helium-7 and helium-8 are hyperfragments that are created in certain Nuclear Reaction s. Precautions The voice of a person who has inhaled helium temporarily sounds high-pitched, resembling those of the of the Vocal Cords remains more or less the same. Although the vocal effect of inhaling helium may be amusing, it can be dangerous if done to excess. The reason is not due to toxicity or any property of helium but simply due to it displacing Oxygen needed for normal Respiration . One must be aware that in Mammals (with the notable exception of Seal s) the breathing reflex is not triggered by insufficient oxygen but rather excess of Carbon Dioxide . Unconsciousness , Brain Damage and even Asphyxiation followed by Death may result in extreme cases. Also, if helium is inhaled directly from pressurized cylinders the high flow rate can fatally rupture Lung tissue. Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in Human Blood . At high pressures, a mixture of helium and oxygen ( Heliox ) can lead to High Pressure Nervous Syndrome ; a small proportion of nitrogen can alleviate the problem. Containers of helium gas at 5 to 10 K should be treated as if they have liquid inside. This is due to the rapid and large increases in Pressure and, if allowed, Volume that occur when helium gas at that temperature is warmed to Room Temperature . References ;Prose Specific references are indicated by comments in the article source
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