Helium
hydrogen ←helium →
lithium
-
七生
↑He ↓Ne
Appearance
Colorless gas, exhibiting a purple glow when placed
in a high voltage electric field
General properties
路亚入门Name,symbol,number helium, He, 2Pronunciation /ˈhi ːliəm/,HEE -lee-əm Element category noble gas Group,period,block
18,1,s
Standard atomic weight 4.002602(2) g·mol −1Electron
configuration 1s 2Electrons per shell 2 (Image)Physical properties Pha gas
Density
(0 °C, 101.325 kPa)0.1786 g/L
From Wikipedia, the free encyclopedia
Helium is the chemical element with atomic number 2 and an atomic weight of 4.0026, which is reprented by the symbol He . It is a colorless, odorless, tasteless, non-toxic,inert monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among the elements and it exists only as a gas except in extreme
conditions. Next to hydrogen, it is the cond most abundant element in the univer, and accounts for 24% of the elemental mass of our galaxy.
An unknown yellow spectral line signature in sunlight was first obrved from a solar eclip in 1868 by French astronomer Pierre Jansn. Jansn is jointly credited with the discovery of the element with Norman Lockyer, who obrved the same eclip and was the first to propo that the line was due to a new element which he named helium. In 1903, large rerves of helium were found in the natural gas fields of the United States, which is by far the largest supplier of the gas.Helium is ud in cryogenics (its largest single u, accounting for about a quarter of production), mostly the cooling of superconducting magnets, particularly the main commercial application in MRI scanners. Helium's
other industrial us as a pressurizing and purge gas, and a protective atmosphere for arc welding and process (such as growing crystals to make silicon wafers), account for half of its u. Economically minor us, such as lifting gas in balloons and airships are popularly known.[2]. Inhaling a small volume of the gas temporarily changes the timbre and quality of the human voice. In
scientific rearch, the behavior of liquid helium-4's two fluid phas, helium I and helium II, is important to rearchers studying quantum mechanics (in particular the phenomenon of superfluidity) and to tho looking at the effects that temperatures near absolute zero have on matter (such as superconductivity).南山佛教文化苑
Helium is the cond lightest element and is the cond most abundant in the obrvable univer, being prent in the univer in mass more than 12 times tho of all the heavier elements combined. Helium's abundance is also similar to this in our own Sun and Jupiter. This high abundance is due to the very high binding energy (per nucleon) of helium-4 with
Periodic table
2He
4/6/2010Helium - Wikipedia, the free encyclop…
0.1786 g/L
Melting point (at 2.5 MPa) 0.95K, −272.20 °C, −457.96 °F
Boiling point 4.22K, −268.93 °C, −452.07 °F Critical point 5.19K, 0.227 MPa Heat of fusion 0.0138kJ·mol −1Heat of
vaporization 0.0829kJ·mol −1
Specific heat capacity
(25 °C) 20.786 J·mol −1·K −1
Vapor pressure (defined by ITS-90)P /Pa 110
100 1 k 10 k 100 k at T /K
1.23
1.67
2.48
4.21
Atomic properties
Electronegativity no data (Pauling scale)Ionization energies
1st: 2372.3kJ·mol −12nd: 5250.5 kJ·mol −1Covalent radius 28 pm
Van der Waals radius
140 pm Miscellanea
Crystal structure hexagonal clo-packed Magnetic ordering diamagnetic [1]
Thermal conductivity (300 K) 0.1513 W·m −1·K −1Speed of sound 972m/s CAS registry number
7440-59-7Most stable isotopes Main article:Isotopes of helium
iso
NA half-life DM DE (MeV)DP
3He
0.000137%*
3He is stable with 1neutron 4He 99.999863%*
4He is stable with 2neutrons
*Atmospheric value, abundance may differ elwhere.
respect to the next three elements after helium (lithium,beryllium, and boron). This helium-4 binding energy also accounts for its commonality as a product in both nuclear fusion and radioactive decay. Most helium in the univer is helium-4, and was formed during the Big Bang. Some new helium is being created prently as a result of the nuclear fusion of hydrogen, in all but the very heaviest stars, which fu helium into heavier elements at the extreme ends of their lives.
On Earth, the lightness of helium has caud its evaporation from the gas and dust cloud from which the planet
condend, and it is thus relatively rare—0.00052% by volume in the atmosphere. What helium is pr
什么的纪律ent today has been mostly created by the natural radioactive decay of heavy radioactive elements (thorium and uranium), as the alpha particles that are emitted by such decays consist of helium-4nuclei. This radiogenic helium is trapped with natural gas in concentrations up to ven percent by volume, from which it is extracted commercially by a low-temperature paration process called fractional distillation.
Contents
1History
1.1Scientific discoveries 1.2Extraction and u
2Characteristics
2.1The helium atom
2.1.1Helium in quantum mechanics 2.1.2The related stability of the helium-4 nucleus and electron shell
2.2Gas and plasma phas 2.3Solid and liquid phas
2.3.1Helium I state 2.3.2Helium II state 3Isotopes 4Compounds
5Occurrence and production
5.1Natural abundance 5.2Modern extraction 5.3Supply depletion 6Applications 7Safety
4/6/2010Helium - Wikipedia, the free encyclop…
枸杞和茶叶能一起泡吗Spectral lines of helium
8Biological effects 9See also 10Notes 11References 12External links
History
Scientific discoveries
The first evidence of helium was obrved on August 18, 1868 as a bright yellow line with a wavelength of
587.49 nanometers in the spectrum of the chromosphere of the Sun. The line was detected by French astronomer Pierre Jansn during a total solar eclip in Guntur,India.[3][4] This line was initially assumed to be sodium. On October 20 of the same year, English astronomer Norman Lockyer obrved a yellow line in the solar spectrum,which he named the D 3Fraunhofer line becau it was near the known D 1 and D 2 lines of sodium.[5] He concluded that it was caud by an element in the Sun unknown on Earth. Lockyer and English chemist Edward Frankland named the element with the Greek word for the Sun,ἥλιος (helios )."[6][7][8]
In 1882, Italian physicist Luigi Palmieri detected helium on Earth, for the first time, through its D 3 spectral line, when he analyzed the lava of Mount Vesuvius.[9]
On March 26, 1895 British chemist Sir William Ramsay isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10%
rare earth elements) with mineral acids. Ramsay was looking for argon but, after parating nitrogen and oxygen from the gas liberated by sulfuric acid, he noticed a bright yellow line that matched the D 3 line obrved in the
spectrum of the Sun.[5][10][11][12] The samples were identified as helium by Lockyer and British p
hysicist William Crookes. It was independently isolated from cleveite in the same year by chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, who collected enough of the gas to accurately determine its atomic weight.[4][13][14]Helium was also isolated by the American geochemist William Francis Hillebrand prior to Ramsay's discovery when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to nitrogen. His letter of congratulations to Ramsay offers an interesting ca of discovery and near-discovery in science.[15]滋补羊汤
In 1907,Ernest Rutherford and Thomas Royds demonstrated that alpha particles are helium nuclei by allowing the particles to penetrate the thin glass wall of an evacuated tube, then creating a discharge in the tube to study the spectra of the new gas inside. In 1908, helium was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than one kelvin.[16] He tried to solidify it by further reducing the temperature but failed
becau helium does not have a triple point temperature at which the solid, liquid, and gas phas are at equilibrium.Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm 3 of helium in 1926.[17]
电脑基础学习In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at
temperatures near absolute zero, a phenomenon now called superfluidity.[18] This phenomenon is related to Bo-Einstein condensation. In 1972, the same phenomenon was obrved in helium-3, but at temperatures much clor to absolute zero, by American physicists Douglas D. Osheroff,David M. Lee, and Robert C. Richardson. The
phenomenon in helium-3 is thought to be related to pairing of helium-3fermions to make bosons, in analogy to Cooper pairs of electrons producing superconductivity.[19]
Extraction and u
After an oil drilling operation in 1903 in Dexter,Kansas produced a gas geyr that would not burn, Kansas state geologist Erasmus Haworth collected samples of the escaping gas and took them back to the University of Kansas at Lawrence where, with the help of chemists Hamilton Cady and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15%methane (a combustible percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas.[4][20] With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was heli
um.[21][22] This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the American Great Plains, available for extraction as a byproduct of natural gas.[23] The greatest rerves of helium were in the Hugoton and nearby gas fields in southwest Kansas and the panhandles of Texas and Oklahoma.
This enabled the United States to become the world's leading supplier of helium. Following a suggestion by Sir Richard Threlfall, the United States Navy sponsored three small experimental helium production plants during World War I. The goal was to supply barrage balloons with the non-flammable, lighter-than-air gas. A total of
5,700 m3 (200,000 cubic feet) of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained.[5] Some of this gas was ud in the world's first helium-filled airship, 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 1, 1921.[24]
酸辣凤爪的做法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 ud as a lifting gas in lighter-than-air craft. This u incread demand during World War II, as well as demands for shiel
ded arc welding. The helium mass spectrometer was also vital in the atomic bomb Manhattan Project.[25]
The government of the United States t up the National Helium Rerve in 1925 at Amarillo,Texas with the goal of supplying military airships in time of war and commercial airships in peacetime.[5] Due to a US military embargo against Germany that restricted helium supplies, the Hindenburg was forced to u hydrogen as the lift gas. Helium u following World War II was depresd but the rerve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other us) during the Space Race and Cold War. Helium u in the United States in 1965 was more than eight times the peak wartime consumption.[26]
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 conrvation program, the Bureau built a 425-mile (684 km) pipeline from Bushton,Kansas to connect tho plants with the government's partially depleted Cliffside gas field, near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, when it then was further purified.[27]
By 1995, a billion cubic meters of the gas had been collected and the rerve was US$1.4 billion in debt, prompting the Congress of the United States in 1996 to pha out the rerve.[4][28] The resulting "Helium Privatization Act of 1996"[29] (Public Law 104–273) directed the United States Department of the Interior to start emptying the rerve by 2005.[30]
Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships.
