Helium (He)
noble-gasGas
Peso atomico standard
4,002602 uConfigurazione elettronica
1s2Punto di fusione
-272,2 °CPunto di ebollizione
-268,93 °CDensità
0,1785 kg/m³Stati di ossidazione
0Elettronegatività (Pauling)
N/DEnergia di ionizzazione (1ª)
24,587389 eVAnno della scoperta
1868Raggio atomico
120 pmDettagli
Helium is a noble gas and the second element in the periodic table. It is chemically inert under ordinary conditions because its 1s electron shell is filled, and it exists as monatomic He rather than as a molecule. Its low density, very low boiling point, high thermal conductivity, and nonflammability make it technologically important. On Earth it is uncommon in the atmosphere but can accumulate in some natural gas reservoirs through radioactive decay of uranium and thorium.
Helium has the lowest melting point of any element and is widely used in cryogenic research because its boiling point is close to absolute zero. Also, the element is vital in the study of super conductivity.
Using liquid helium, Kurti, co-workers and others have succeeded in obtaining temperatures of a few microkelvins by the adiabatic demagnetization of copper nuclei.
Helium has other peculiar properties: It is the only liquid that cannot be solidified by lowering the temperature. It remains liquid down to absolute zero at ordinary pressures, but will readily solidify by increasing the pressure. Solid 3He and 4He are unusual in that both can be changed in volume by more than 30% by applying pressure.
The specific heat of helium gas is unusually high. The density of helium vapor at the normal boiling point is also very high, with the vapor expanding greatly when heated to room temperature. Containers filled with helium gas at 5 to 10 K should be treated as though they contained liquid helium due to the large increase in pressure resulting from warming the gas to room temperature.
While helium normally has a 0 valence, it seems to have a weak tendency to combine with certain other elements. Means of preparing helium difluoride have been studied, and species such as HeNe and the molecular ions He+ and He++ have been investigated.
The name derives from the Greek helios for "sun". The element was discovered by spectroscopy during a solar eclipse in the sun's chromosphere by the French astronomer Pierre-Jules-Cesar Janssen in 1868. It was independently discovered and named helium by the English astronomer Joseph Norman Lockyer.
Helium was thought to be only a solar constituent until it was later found to be identical to the helium in the uranium ore cleveite by the Scottish chemist William Ramsay in 1895. The Swedish chemists Per Theodore Cleve and Nils Abraham Langet independently found helium in cleveite at about the same time.
Helium, the second most abundant element in the universe, was discovered on the sun before it was found on the earth. Pierre-Jules-César Janssen, a French astronomer, noticed a yellow line in the sun's spectrum while studying a total solar eclipse in 1868. Sir Norman Lockyer, an English astronomer, realized that this line, with a wavelength of 587.49 nanometers, could not be produced by any element known at the time. It was hypothesized that a new element on the sun was responsible for this mysterious yellow emission. This unknown element was named helium by Lockyer. The hunt to find helium on earth ended in 1895. Sir William Ramsay, a Scottish chemist, conducted an experiment with a mineral containing uranium called clevite. He exposed the clevite to mineral acids and collected the gases that were produced. He then sent a sample of these gases to two scientists, Lockyer and Sir William Crookes, who were able to identify the helium within it. Two Swedish chemists, Nils Langlet and Per Theodor Cleve, independently found helium in clevite at about the same time as Ramsay.
Helium makes up about 0.0005% of the earth's atmosphere. This trace amount of helium is not gravitationally bound to the earth and is constantly lost to space. The earth's atmospheric helium is replaced by the decay of radioactive elements in the earth's crust. Alpha decay, one type of radioactive decay, produces particles called alpha particles. An alpha particle can become a helium atom once it captures two electrons from its surroundings. This newly formed helium can eventually work its way to the atmosphere through cracks in the crust.
From the Greek word helios, the sun. Janssen obtained the first evidence of helium during the solar eclipse of 1868 when he detected a new line in the solar spectrum. Lockyer and Frankland suggested the name helium for the new element. In 1895 Ramsay discovered helium in the uranium mineral cleveite while it was independently discovered in cleveite by the Swedish chemists Cleve and Langlet at about the same time. Rutherford and Royds in 1907 demonstrated that alpha particles are helium nuclei.
Pure helium is a colorless, odorless, tasteless gas at ordinary temperature and pressure. It liquefies only at very low temperature and does not freeze at normal pressure, remaining liquid down to absolute zero unless compressed. Liquid helium is clear and highly mobile.
Helium is used where an inert, light, and very cold fluid is needed. Liquid helium cools superconducting magnets in magnetic resonance imaging, particle accelerators, and low-temperature research. Gaseous helium is used as a shielding gas in specialized welding, as a leak-detection tracer, as a pressurizing and purging gas for rockets and cryogenic systems, and as a carrier gas in gas chromatography. Helium also fills balloons and airships when nonflammability is more important than lift efficiency. Helium-3 is used in neutron detection, cryogenic research, and some specialized physics experiments, but its supply is limited.
Helium is commercially recovered from natural gas deposits, mostly from Texas, Oklahoma and Kansas. Helium gas is used to inflate blimps, scientific balloons and party balloons. It is used as an inert shield for arc welding, to pressurize the fuel tanks of liquid fueled rockets and in supersonic windtunnels. Helium is combined with oxygen to create a nitrogen free atmosphere for deep sea divers so that they will not suffer from a condition known as nitrogen narcosis. Liquid helium is an important cryogenic material and is used to study superconductivity and to create superconductive magnets. The Department of Energy's Jefferson Lab uses large amounts of liquid helium to operate its superconductive electron accelerator.
Helium is an inert gas and does not easily combine with other elements. There are no known compounds that contain helium, although attempts are being made to produce helium diflouride (HeF2).
▸ as an inert gas shield for arc welding;
▸ a protective gas in growing silicon and germanium crystals and producing titanium and zirconium;
▸ as a cooling medium for nuclear reactors, and
▸ as a gas for supersonic wind tunnels.
A mixture of helium and oxygen is used as an artificial atmosphere for divers and others working under pressure. Different ratios of He and O2 are used for different diver operation depths.
Helium is extensively used for filling balloons as it is a much safer gas than hydrogen. One of the recent largest uses for helium has been for pressuring liquid fuel rockets. A Saturn booster, like the type used on the Apollo lunar missions, required about 13 million ft3 of helium for a firing, plus more for checkouts.
Liquid helium's use in magnetic resonance imaging (MRI) continues to increase as the medical profession accepts and develops new uses for the equipment. This equipment has eliminated some need for exploratory surgery by accurately diagnosing patients. Another medical application uses MRE to determine (by blood analysis) whether a patient has any form of cancer.
Helium is also being used to advertise on blimps for various companies, including Goodyear. Other lifting gas applications are being developed by the Navy and Air Force to detect low-flying cruise missiles. Additionally, the Drug Enforcement Agency is using radar-equipped blimps to detect drug smugglers along the United States boarders. In addition, NASA is currently using helium-filled balloons to sample the atmosphere in Antarctica to determine what is depleting the ozone layer.
Isotopes in Geochronology
3He is a product of the radioactive decay of 3H (half-life of 12.31 years). The relative variations in the amount ratio n(3He)/n(3H) can be interpreted in terms of elapsed time. This has been especially useful in aquatic systems, including oceans, lakes, and aquifers, that received large inputs of 3H from precipitation following thermonuclear bomb test periods. 3H- 3He dating provides the elapsed time since a water mass became isolated from the atmosphere in the time range from the mid-1950s to the present. Such studies are important for establishing the sustainability of groundwater resources in shallow aquifers [27] D. K. Solomon, P. G. Cook. “3H and 3He”, in Environmental Tracers in Subsurface Hydrology, P. G. Cook and A. L. Herczeg (Eds.), Kluwer Academic Publishers, Boston (2000)., [28] P. Schlosser, M. Stute, H. Dörr, C. Sonntag, K. O. Münnich. Earth Planet. Sci. Lett.89, 353 (1988)..
4He is a product of radioactive decay in the uranium and thorium decay series. As a result, 4He concentration is used to estimate the relative ages of minerals and groundwater. In closed systems (systems that do not exchange matter with their surroundings), relative variations in the amount ratio n(4He)/n(U) can be interpreted in terms of elapsed time, although other processes can alter the distribution of helium, which is highly mobile in terrestrial environments [29] M. Ozima, F. A. Podosek. Noble Gas Geochemistry: 2nd Edition, p. 286, Cambridge University Press, Cambridge, UK (2002)., [30] D. K. Solomon. “4He in groundwater”, in Environmental Tracers in Subsurface Hydrology, P. G. Cook and A. L. Herczeg (Eds.), Kluwer Academic Publishers, Boston (2000)..
4He concentrations commonly increase along groundwater flow paths through a cumulative release from aquifer materials. This rate of accumulation is used to estimate the time since the groundwater was recharged at the surface. The 4He accumulation method of groundwater dating is typically used in deeper aquifers, where groundwater is relatively old and the 3H- 3He method cannot be used because of the relatively short half-life of 12.31 years for 3H [30] D. K. Solomon. “4He in groundwater”, in Environmental Tracers in Subsurface Hydrology, P. G. Cook and A. L. Herczeg (Eds.), Kluwer Academic Publishers, Boston (2000)..
Isotopes in Industry
3He has a large absorption cross section for neutrons, which makes it especially useful for radioactivity detection [31] D. Kramer. Phys. Today63, 22 (2010)., [32] G. V. Jean. Advancing Hidden Nuclear Material Detection, National Defense Industrial Association (2014), Feb. 28; http://www.nationaldefensemagazine.org/archive/2010/December/Pages/AdvancingHiddenNuclearMaterialDetection.aspx.. In this application, neutrons produced by the radioactive decay of elements, such as uranium and plutonium, enter the detector, where the reaction 3He (n, p) 3H produces 1H and 3H atoms. This induces further collisions and the release of electrons, which interact with charged surfaces to generate an electric current. Large amounts of 3He are used to produce neutron detectors in portal monitors for detecting illicit radioactive materials at ports, border crossings, and airports (Fig. IUPAC.2.1). Unfortunately, the isotope 3He is rare and there is a need to incorporate alternative gases for use in neutron detectors. 3He neutron detectors are also used in devices that determine the proportions of water, oil, and gas in wells drilled for energy production. Other important uses of 3He include lasers, gyroscopes used for missile stability and guidance, and cryogenic research (ultra-low temperature, less than 1 K).
The global supply of 3He available for research and practical applications has become severely limited in recent years, such that prices have increased substantially and some uses have been curtailed [31] D. Kramer. Phys. Today63, 22 (2010)., [32] G. V. Jean. Advancing Hidden Nuclear Material Detection, National Defense Industrial Association (2014), Feb. 28; http://www.nationaldefensemagazine.org/archive/2010/December/Pages/AdvancingHiddenNuclearMaterialDetection.aspx.. A major source of 3He is from nuclear weapons containing 3H, recovered when the warheads are reconditioned or dismantled. 3He accumulates in such devices as a radiogenic product of 3H decay. The annual supply of new 3He has decreased with reductions in nuclear arsenals.
Isotopes in Medicine
3He is used as an inhalant to improve magnetic resonance imaging (MRI) of the lungs [34] M. Ebert, T. Grossmann, W. Heil, E. W. Otten, R. Surkau, M. Thelen, M. Leduc, P. Bachert, M. V. Knopp, L. R. Schad. Lancet347, 1297 (1996)..
Helium has no stable neutral compounds under ordinary chemical conditions. Its closed-shell atom has an extremely high ionization energy and very low polarizability, so conventional covalent or ionic chemistry is absent. Excited helium can form transient species such as the helium dimer ion He₂⁺ and excimers in plasmas. Under high pressure, helium can enter crystalline inclusion compounds and van der Waals solids; sodium helide, often written Na₂He, has been reported as a high-pressure electride rather than a normal valence compound. These phases are not examples of everyday helium chemistry.
See more information at the Helium compound page.
Helium is not toxic and is not flammable, but it can displace oxygen in confined spaces and cause asphyxiation without warning. Compressed helium cylinders present mechanical hazards if mishandled. Liquid helium can cause severe cold burns and can rapidly expand to large gas volumes, creating pressure and oxygen-deficiency risks. Inhalation to alter the voice is dangerous because it can deprive the body of oxygen or cause pressure injury from cylinders.
Most terrestrial helium is produced by alpha decay in rocks; alpha particles become helium nuclei and then neutral atoms. Because helium is light and unreactive, it migrates through rocks, dissolves only weakly in water, and eventually escapes from the atmosphere to space. Commercially recoverable accumulations require suitable source rocks and trapping structures, often associated with natural gas fields. Helium has no known biological requirement and little direct chemical ecological effect.
Helium is recovered chiefly as a by-product from natural gas streams that contain unusually high helium concentrations. Separation commonly uses cryogenic processing, pressure-swing adsorption, or membrane methods after removal of major gases. Supply is constrained by geology, gas-field development, purification capacity, storage, and transport of either compressed gas or cryogenic liquid. Demand is led by cryogenics, especially superconducting magnets, with additional use in leak detection, analytical instrumentation, welding, and aerospace systems. Recycling is technically valuable in laboratories and large facilities but is not universal, because capture and reliquefaction require specialized equipment.
Except for hydrogen, helium is the most abundant element found in the universe. Helium is extracted from natural gas. In fact, all natural gas contains at least trace quantities of helium.
It has been detected spectroscopically in great abundance, especially in the hotter stars, and it is an important component in both the proton-proton reaction and the carbon cycle, which account for the energy of the sun and stars.
The helium content of the atmosphere is about 1 part in 200,000. While it is present in various radioactive minerals as a decay product, the bulk of the Free World's supply is obtained from wells in Texas, Oklahoma, and Kansas. Outside the United States, the only known helium extraction plants, in 1984 were in Eastern Europe (Poland), the USSR, and a few in India.
Helium is one of the most abundant elements in the universe. Most ⁴He was formed during Big Bang nucleosynthesis, and more is produced by hydrogen fusion in stars. It is a major constituent of the Sun and gas giant planets. On rocky planets, atmospheric helium is usually depleted because neutral helium can escape gravitationally over geologic time.
- Helium was first identified in the solar spectrum before it was isolated on Earth.
- At normal pressure, helium is the only element that does not solidify by cooling alone.
- Liquid ⁴He becomes a superfluid below the lambda point near 2.17 K.
- Helium has a negative Joule-Thomson coefficient above its inversion temperature, so it can warm during throttling at the
Immagini
Proprietà
Fisiche
- Raggio atomico (empirico)
- 120 pm Confronta Raggio atomico (empirico) di tutti gli elementi →
- Raggio covalente
- 28 pm Confronta Raggio covalente di tutti gli elementi →
- Raggio di van der Waals
- 140 pm Confronta Raggio di van der Waals di tutti gli elementi →
- Densità
- 0,1785 kg/m³ Confronta Densità di tutti gli elementi →
- Volume molare
- 0,0318 L/mol
- Fase in condizioni STP
- Gas Confronta Fase in condizioni STP di tutti gli elementi →
- Punto di fusione
- -272,2 °C Confronta Punto di fusione di tutti gli elementi →
- Punto di ebollizione
- -268,93 °C Confronta Punto di ebollizione di tutti gli elementi →
- Conducibilità termica
- 0,152 W/(m·K) Confronta Conducibilità termica di tutti gli elementi →
- Capacità termica specifica
- 5,193 J/(g·K) Confronta Capacità termica specifica di tutti gli elementi →
- Capacità termica molare
- 20,786 J/(mol·K) Confronta Capacità termica molare di tutti gli elementi →
- Struttura cristallina
- Esagonale compatta Confronta Struttura cristallina di tutti gli elementi →
Chimiche
- Elettronegatività (Allen)
- 4,16
- Affinità elettronica
- -0,5 eV (valore negativo — l'atomo non dovrebbe legare un elettrone extra)
- Energia di ionizzazione (1ª)
- 24,587389 eV Confronta Energia di ionizzazione (1ª) di tutti gli elementi →
- Energia di ionizzazione (2ª)
- 54,417953 eV Confronta Energia di ionizzazione (2ª) di tutti gli elementi →
- Stati di ossidazione
- 0 Confronta Stati di ossidazione di tutti gli elementi →
- Elettroni di valenza
- 2 Confronta Elettroni di valenza di tutti gli elementi →
- Configurazione elettronica
- 1s2
Termodinamiche
- Punto triplo (temperatura)
- -270,973 °C
- Punto triplo (pressione)
- 5043 Pa
- Punto critico (temperatura)
- -267,955 °C
- Punto critico (pressione)
- 2,2746e+5 Pa
- Calore di fusione
- 1,430274e-4 eV Confronta Calore di fusione di tutti gli elementi →
- Calore di vaporizzazione
- 8,291444e-4 eV Confronta Calore di vaporizzazione di tutti gli elementi →
- Calore di atomizzazione
- 0 eV
Nucleari
- Protoni
- 2 Confronta Protoni di tutti gli elementi →
- Neutroni
- 2 Confronta Neutroni di tutti gli elementi →
- Isotopi noti
- 8 Confronta Isotopi noti di tutti gli elementi →
- Isotopi stabili
- 2 Confronta Isotopi stabili di tutti gli elementi →
- Isotopo più stabile
- He-4
- Anno della scoperta
- 1868
Abbondanza
- Abbondanza (crosta terrestre)
- 0,008 mg/kg Confronta Abbondanza (crosta terrestre) di tutti gli elementi →
- Abbondanza (oceano)
- 7 × 10−6 mg/L Confronta Abbondanza (oceano) di tutti gli elementi →
Struttura cristallina
- Costante reticolare a
- 357 pm
Struttura elettronica
- Elettroni per guscio
- 2 Confronta Elettroni per guscio di tutti gli elementi →
Identificativi
- Numero CAS
- 7440-59-7 Confronta Numero CAS di tutti gli elementi →
- Simbolo di termine
- 1S0
- InChI
- InChI=1S/He
- Chiave InChI
- SWQJXJOGLNCZEY-UHFFFAOYSA-N
Configurazione elettronica Misurato
He: 1s²1s²1s²Modello atomico
Gli isotopi modificano il numero di neutroni, la massa e la stabilità — non la configurazione elettronica di un atomo neutro.
Modello atomico schematico, non in scala.
Impronta atomica
Spettro di emissione / assorbimento
Distribuzione isotopica
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita |
|---|---|---|---|
| 3 Stabile | 3,0160293201 ± 0,0000000025 | 0,0001% | Stabile |
| 4 Stabile | 4,00260325413 ± 0,00000000006 | 99,9999% | Stabile |
Fase / Stato
Motivo: 293,9 °C sopra il punto di ebollizione (-268,93 °C)
Schema non in scala
Punti di transizione di fase
Energie di transizione
Energia necessaria per fondere 1 mol al punto di fusione
Energia necessaria per vaporizzare 1 mol al punto di ebollizione
Densità
In condizioni standard
Stimata con la legge dei gas ideali alla T attuale
Avanzate
Spettri atomici
Righe disponibili ?
| Ione | Carica | Righe totali | Probabilità di transizione | Designazioni dei livelli |
|---|---|---|---|---|
| 3He I Isotopo | 0 | 2289 | 0 | 2289 |
| He I | 0 | 2300 | 2289 | 2300 |
| He II | +1 | 140 | 140 | 140 |
| 3He II Isotopo | +1 | 140 | 140 | 140 |
Livelli disponibili ?
| Ione | Carica | Livelli |
|---|---|---|
| 3He I Isotopo | 0 | 188 |
| He I | 0 | 843 |
| He II | +1 | 149 |
| 3He II Isotopo | +1 | 149 |
Composti
Isotopi (2)
Seven isotopes of helium are known: Liquid helium (He-4) exists in two forms: He-4I and He-4II, with a sharp transition point at 2.174K. He-4I (above this temperature) is a normal liquid, but He-4II (below it) is unlike any other known substance. It expands on cooling, its conductivity for heat is enormous, and neither its heat conduction nor viscosity obeys normal rules.
| Numero di massa | Massa atomica (u) | Abbondanza naturale | Emivita | Modalità di decadimento | |
|---|---|---|---|---|---|
| 3 Stabile | 3,0160293201 ± 0,0000000025 | 0,0001% ± 0,0000% | Stabile | stable | |
| 4 Stabile | 4,00260325413 ± 0,00000000006 | 99,9999% ± 0,0000% | Stabile | stable |
Righe spettrali
| Lunghezza d'onda (nm) | Intensità | Stadio di ionizzazione | Tipo | Transizione | Accuratezza | Fonte | |
|---|---|---|---|---|---|---|---|
| 381.9601975 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 381.9602773 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 381.9602828 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 381.9613129 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 381.9613927 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 381.975731 nm | 1 | He I | emission | 1s.2p 3P* → 1s.6d 3D | Misurata | NIST | |
| 383.3548713 nm | 0 | He I | emission | 1s.2p 1P* → 1s.10d 1D | Misurata | NIST | |
| 383.8100125 nm | N/D | He I | emission | 1s.2p 1P* → 1s.10s 1S | Misurata | NIST | |
| 386.7472343 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6s 3S | Misurata | NIST | |
| 386.7483778 nm | N/D | He I | emission | 1s.2p 3P* → 1s.6s 3S | Misurata | NIST | |
| 386.7631595 nm | 1 | He I | emission | 1s.2p 3P* → 1s.6s 3S | Misurata | NIST | |
| 387.1786406 nm | 1 | He I | emission | 1s.2p 1P* → 1s.9d 1D | Misurata | NIST | |
| 387.8176858 nm | N/D | He I | emission | 1s.2p 1P* → 1s.9s 1S | Misurata | NIST | |
| 388.8604644 nm | N/D | He I | emission | 1s.2s 3S → 1s.3p 3P* | Misurata | NIST | |
| 388.864559 nm | N/D | He I | emission | 1s.2s 3S → 1s.3p 3P* | Misurata | NIST | |
| 388.8648915 nm | N/D | He I | emission | 1s.2s 3S → 1s.3p 3P* | Misurata | NIST | |
| 392.6544387 nm | 1 | He I | emission | 1s.2p 1P* → 1s.8d 1D | Misurata | NIST | |
| 393.5945223 nm | 0 | He I | emission | 1s.2p 1P* → 1s.8s 1S | Misurata | NIST | |
| 396.4728829 nm | 20 | He I | emission | 1s.2s 1S → 1s.4p 1P* | Misurata | NIST | |
| 397.2015454 nm | N/D | He I | emission | 1s.2s 1S → 1s.4d 1D | Misurata | NIST | |
| 400.9256516 nm | 1 | He I | emission | 1s.2p 1P* → 1s.7d 1D | Misurata | NIST | |
| 402.3979795 nm | 1 | He I | emission | 1s.2p 1P* → 1s.7s 1S | Misurata | NIST | |
| 402.6184368 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 402.6185901 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 402.6186005 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 402.619676 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 402.6198294 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 402.6356959 nm | 5 | He I | emission | 1s.2p 3P* → 1s.5d 3D | Misurata | NIST | |
| 412.0810765 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5s 3S | Misurata | NIST | |
| 412.0823747 nm | N/D | He I | emission | 1s.2p 3P* → 1s.5s 3S | Misurata | NIST | |
| 412.0991564 nm | 2 | He I | emission | 1s.2p 3P* → 1s.5s 3S | Misurata | NIST | |
| 414.1332157 nm | N/D | He I | emission | 1s.2p 1P* → 1s.6p 1P* | Misurata | NIST | |
| 414.3759059 nm | 3 | He I | emission | 1s.2p 1P* → 1s.6d 1D | Misurata | NIST | |
| 416.8971512 nm | 1 | He I | emission | 1s.2p 1P* → 1s.6s 1S | Misurata | NIST | |
| 438.3278555 nm | N/D | He I | emission | 1s.2p 1P* → 1s.5p 1P* | Misurata | NIST | |
| 438.7929143 nm | 10 | He I | emission | 1s.2p 1P* → 1s.5d 1D | Misurata | NIST | |
| 443.7553428 nm | 3 | He I | emission | 1s.2p 1P* → 1s.5s 1S | Misurata | NIST | |
| 447.1470373 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 447.1474077 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 447.1474317 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 447.1485658 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 447.1489362 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 447.1683251 nm | 25 | He I | emission | 1s.2p 3P* → 1s.4d 3D | Misurata | NIST | |
| 468.537685 nm | N/D | He II | emission | 3p 2P* → 4d 2D | Misurata | NIST | |
| 468.5407226 nm | N/D | He II | emission | 3s 2S → 4p 2P* | Misurata | NIST | |
| 468.5524404 nm | N/D | He II | emission | 3p 2P* → 4s 2S | Misurata | NIST | |
| 468.5568006 nm | N/D | He II | emission | 3s 2S → 4p 2P* | Misurata | NIST | |
| 468.570385 nm | N/D | He II | emission | 3d 2D → 4f 2F* | Misurata | NIST | |
| 468.570438 nm | N/D | He II | emission | 3p 2P* → 4d 2D | Misurata | NIST | |
| 468.575708 nm | N/D | He II | emission | 3d 2D → 4p 2P* | Misurata | NIST | |
| 468.5757975 nm | N/D | He II | emission | 3p 2P* → 4d 2D | Misurata | NIST | |
| 468.5804092 nm | N/D | He II | emission | 3d 2D → 4f 2F* | Misurata | NIST | |
| 468.583089 nm | N/D | He II | emission | 3d 2D → 4f 2F* | Misurata | NIST | |
| 468.5884123 nm | N/D | He II | emission | 3d 2D → 4p 2P* | Misurata | NIST | |
| 468.5905553 nm | N/D | He II | emission | 3p 2P* → 4s 2S | Misurata | NIST | |
| 468.5917885 nm | N/D | He II | emission | 3d 2D → 4p 2P* | Misurata | NIST | |
| 471.3139173 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4s 3S | Misurata | NIST | |
| 471.3156155 nm | N/D | He I | emission | 1s.2p 3P* → 1s.4s 3S | Misurata | NIST | |
| 471.3375684 nm | 4 | He I | emission | 1s.2p 3P* → 1s.4s 3S | Misurata | NIST | |
| 491.074748 nm | N/D | He I | emission | 1s.2p 1P* → 1s.4p 1P* | Misurata | NIST | |
| 492.0612726 nm | N/D | He I | emission | 1s.2p 1P* → 1s.4f 1F* | Misurata | NIST | |
| 492.1931036 nm | 20 | He I | emission | 1s.2p 1P* → 1s.4d 1D | Misurata | NIST | |
| 501.567801 nm | 100 | He I | emission | 1s.2s 1S → 1s.3p 1P* | Misurata | NIST | |
| 504.208749 nm | N/D | He I | emission | 1s.2s 1S → 1s.3d 1D | Misurata | NIST | |
| 504.773857 nm | 10 | He I | emission | 1s.2p 1P* → 1s.4s 1S | Misurata | NIST | |
| 587.443388 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 1D | Misurata | NIST | |
| 587.446026 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 1D | Misurata | NIST | |
| 587.559871 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 587.561397 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 587.561484 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 587.56251 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 587.564036 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 587.596628 nm | 100 | He I | emission | 1s.2p 3P* → 1s.3d 3D | Misurata | NIST | |
| 655.976872 nm | N/D | He II | emission | 4p 2P* → 6d 2D | Misurata | NIST | |
| 655.979395 nm | N/D | He II | emission | 4s 2S → 6p 2P* | Misurata | NIST | |
| 655.98544 nm | N/D | He II | emission | 4p 2P* → 6s 2S | Misurata | NIST | |
| 655.988733 nm | N/D | He II | emission | 4s 2S → 6p 2P* | Misurata | NIST | |
| 656.005227 nm | N/D | He II | emission | 4d 2D → 6f 2F* | Misurata | NIST | |
| 656.005274 nm | N/D | He II | emission | 4p 2P* → 6d 2D | Misurata | NIST | |
| 656.008318 nm | N/D | He II | emission | 4d 2D → 6p 2P* | Misurata | NIST | |
| 656.008387 nm | N/D | He II | emission | 4p 2P* → 6d 2D | Misurata | NIST | |
| 656.01416 nm | N/D | He II | emission | 4f 2F* → 6g 2G | Misurata | NIST | |
| 656.014176 nm | N/D | He II | emission | 4d 2D → 6f 2F* | Misurata | NIST | |
| 656.015708 nm | N/D | He II | emission | 4f 2F* → 6d 2D | Misurata | NIST | |
| 656.015732 nm | N/D | He II | emission | 4d 2D → 6f 2F* | Misurata | NIST | |
| 656.016955 nm | N/D | He II | emission | 4p 2P* → 6s 2S | Misurata | NIST | |
| 656.017657 nm | N/D | He II | emission | 4d 2D → 6p 2P* | Misurata | NIST | |
| 656.018478 nm | N/D | He II | emission | 4f 2F* → 6g 2G | Misurata | NIST | |
| 656.01882 nm | N/D | He II | emission | 4f 2F* → 6d 2D | Misurata | NIST | |
| 656.018823 nm | N/D | He II | emission | 4d 2D → 6p 2P* | Misurata | NIST | |
| 656.019412 nm | N/D | He II | emission | 4f 2F* → 6g 2G | Misurata | NIST | |
| 656.02096 nm | N/D | He II | emission | 4f 2F* → 6d 2D | Misurata | NIST | |
| 663.190187 nm | N/D | He I | emission | 1s.2p 1P* → 1s.3p 1P* | Misurata | NIST | |
| 667.815174 nm | 100 | He I | emission | 1s.2p 1P* → 1s.3d 1D | Misurata | NIST | |
| 667.967687 nm | N/D | He I | emission | 1s.2p 1P* → 1s.3d 3D | Misurata | NIST | |
| 706.517716 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3s 3S | Misurata | NIST | |
| 706.521532 nm | N/D | He I | emission | 1s.2p 3P* → 1s.3s 3S | Misurata | NIST | |
| 706.570863 nm | 30 | He I | emission | 1s.2p 3P* → 1s.3s 3S | Misurata | NIST | |
| 716.055563 nm | N/D | He I | emission | 1s.3s 3S → 1s.10p 3P* | Misurata | NIST | |
| 716.055907 nm | N/D | He I | emission | 1s.3s 3S → 1s.10p 3P* | Misurata | NIST | |
| 716.055935 nm | N/D | He I | emission | 1s.3s 3S → 1s.10p 3P* | Misurata | NIST | |
| 728.13508 nm | 50 | He I | emission | 1s.2p 1P* → 1s.3s 1S | Misurata | NIST | |
| 729.803204 nm | N/D | He I | emission | 1s.3s 3S → 1s.9p 3P* | Misurata | NIST | |
| 729.803696 nm | N/D | He I | emission | 1s.3s 3S → 1s.9p 3P* | Misurata | NIST | |
| 729.803736 nm | N/D | He I | emission | 1s.3s 3S → 1s.9p 3P* | Misurata | NIST | |
| 749.984714 nm | N/D | He I | emission | 1s.3s 3S → 1s.8p 3P* | Misurata | NIST | |
| 749.985457 nm | N/D | He I | emission | 1s.3s 3S → 1s.8p 3P* | Misurata | NIST | |
| 749.985518 nm | N/D | He I | emission | 1s.3s 3S → 1s.8p 3P* | Misurata | NIST |
Proprietà estese
Raggi covalenti (dati estesi)
- Raggio covalente (Pyykkö)
- 46 pm
Raggi di van der Waals
- Bondi
- 140 pm
- Alvarez
- 143 pm
- UFF
- 236,2 pm
- MM3
- 153 pm
Raggi atomici e metallici
- Raggio atomico (Rahm)
- 134 pm
- Raggio metallico (C12)
- 122 pm
Scale di numerazione
- Mendeleev
- 112
- Pettifor
- 1
- Glawe
- 1
Scale di elettronegatività
- Ghosh
- 0
- Gunnarsson–Lundqvist
- 8
- Robles–Bartolotti
- 8
Polarizzabilità e dispersione
- Polarizzabilità dipolare
- 1,3838 a.u.
- Polarizzabilità dipolare (inc.)
- 0 a.u.
- C₆
- 1,42 Ha·Bohr6
- C₆ (Gould–Bučko)
- 1,47 Ha·Bohr6
Affinità chimica
- Affinità protonica
- 177,8 kJ/mol
- Basicità in fase gassosa
- 148,5 kJ/mol
Rischio di approvvigionamento ed economia
- Concentrazione della produzione
- 22
- Rischio relativo di approvvigionamento
- 7
- Distribuzione delle riserve
- 21
- Stabilità politica (principale produttore)
- 57
- Stabilità politica (principale detentore di riserve)
- 57
Proprietà dei gas nobili
Transizioni di fase e allotropi
| Punto di ebollizione | 4,22 K |
| Punto critico (temperatura) | 5,19 K |
| Punto critico (pressione) | 0,23 MPa |
| Punto triplo (temperatura) | 2,18 K |
| Punto triplo (pressione) | 5,04 kPa |
Dati di riferimento avanzati
Costanti di schermaggio (1)
| n | Orbitale | σ |
|---|---|---|
| 1 | s | 0,3125 |
Modalità di decadimento degli isotopi (9)
| Isotopo | Modalità | Intensità |
|---|---|---|
| 5 | n | 100% |
| 6 | B- | 100% |
| 6 | B-d | 0% |
| 7 | n | 100% |
| 8 | B- | 100% |
| 8 | B-n | 16% |
| 8 | B-t | 0,9% |
| 9 | n | 100% |
| 10 | 2n | 100% |
Fattori di diffusione dei raggi X (501)
| Energia (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 0 |
| 10,1617 | — | 0 |
| 10,3261 | — | 0 |
| 10,4931 | — | 0 |
| 10,6628 | — | 0 |
| 10,8353 | — | 0 |
| 11,0106 | — | 0 |
| 11,1886 | — | 0 |
| 11,3696 | — | 0 |
| 11,5535 | — | 0 |
Dati aggiuntivi
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
8×10-3 milligrams per kilogram
Riferimenti (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
7×10-6 milligrams per liter
Riferimenti (1)
Sources
Sources of this element.
Except for hydrogen, helium is the most abundant element found in the universe. Helium is extracted from natural gas. In fact, all natural gas contains at least trace quantities of helium.
It has been detected spectroscopically in great abundance, especially in the hotter stars, and it is an important component in both the proton-proton reaction and the carbon cycle, which account for the energy of the sun and stars.
The helium content of the atmosphere is about 1 part in 200,000. While it is present in various radioactive minerals as a decay product, the bulk of the Free World's supply is obtained from wells in Texas, Oklahoma, and Kansas. Outside the United States, the only known helium extraction plants, in 1984 were in Eastern Europe (Poland), the USSR, and a few in India.
Riferimenti (1)
- [6] Helium https://periodic.lanl.gov/2.shtml
Riferimenti
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
Thomas Jefferson National Accelerator Facility (Jefferson Lab) is one of 17 national laboratories funded by the U.S. Department of Energy. The lab's primary mission is to conduct basic research of the atom's nucleus using the lab's unique particle accelerator, known as the Continuous Electron Beam Accelerator Facility (CEBAF). For more information visit https://www.jlab.org/
The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Helium.
The element property data was retrieved from publications.