The intra-aortic balloon pump ( IABP ) is a mechanical device that increases myocardial oxygen perfusion and indirectly increases cardiac output through afterload reduction. It consists of a cylindrical polyurethane balloon that sits in the aorta , approximately 2 centimeters (0.79 in) from the left subclavian artery . The balloon inflates and deflates via counter pulsation, meaning it actively deflates in systole and inflates in diastole . Systolic deflation decreases afterload through a vacuum effect and indirectly increases forward flow from the heart. Diastolic inflation increases blood flow to the coronary arteries via retrograde flow. These actions combine to decrease myocardial oxygen demand and increase myocardial oxygen supply.
136-481: A computer-controlled mechanism inflates the balloon with helium from a cylinder during diastole, usually linked to either an electrocardiogram (ECG) or a pressure transducer at the distal tip of the catheter ; some IABPs, such as the Datascope System 98XT, allow asynchronous counterpulsation at a set rate, though this setting is rarely used. Helium is used to inflate the balloon as its low density means there
272-482: A diamond anvil cell . The insulating electride Na 2 He has been shown to be thermodynamically stable at pressures above 113 GPa. It has a fluorite structure. Chemical element A chemical element is a chemical substance whose atoms all have the same number of protons . The number of protons is called the atomic number of that element. For example, oxygen has an atomic number of 8, meaning each oxygen atom has 8 protons in its nucleus. Atoms of
408-545: A nuclear halo . Table of thermal and physical properties of helium gas at atmospheric pressure: Helium has a valence of zero and is chemically unreactive under all normal conditions. It is an electrical insulator unless ionized . As with the other noble gases, helium has metastable energy levels that allow it to remain ionized in an electrical discharge with a voltage below its ionization potential . Helium can form unstable compounds , known as excimers , with tungsten, iodine, fluorine, sulfur, and phosphorus when it
544-738: A pure element . In chemistry, a pure element means a substance whose atoms all (or in practice almost all) have the same atomic number, or number of protons . Nuclear scientists, however, define a pure element as one that consists of only one isotope. For example, a copper wire is 99.99% chemically pure if 99.99% of its atoms are copper, with 29 protons each. However it is not isotopically pure since ordinary copper consists of two stable isotopes, 69% Cu and 31% Cu, with different numbers of neutrons. However, pure gold would be both chemically and isotopically pure, since ordinary gold consists only of one isotope, Au. Atoms of chemically pure elements may bond to each other chemically in more than one way, allowing
680-441: A superfluid phase, but only at much lower temperatures; as a result, less is known about the properties of the isotope. Helium II is a superfluid, a quantum mechanical state of matter with strange properties. For example, when it flows through capillaries as thin as 10 to 100 nm it has no measurable viscosity . However, when measurements were done between two moving discs, a viscosity comparable to that of gaseous helium
816-424: A beneficiary effect to the struggling heart. It decreases myocardial demand for oxygen and increases coronary flow. Since the device is placed in the femoral artery and aorta it could provoke ischemia , and compartment syndrome . The leg is at highest risk of becoming ischemic if the femoral artery it is supplied by becomes obstructed. Placing the balloon too distal from the aortic arch may induce occlusion of
952-540: A considerable amount of time. (See element naming controversy ). Precursors of such controversies involved the nationalistic namings of elements in the late 19th century. For example, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rights to the French, often calling it cassiopeium . Similarly, the British discoverer of niobium originally named it columbium , in reference to
1088-477: A different element in nuclear reactions , which change an atom's atomic number. Historically, the term "chemical element" meant a substance that cannot be broken down into constituent substances by chemical reactions, and for most practical purposes this definition still has validity. There was some controversy in the 1920s over whether isotopes deserved to be recognized as separate elements if they could be separated by chemical means. The term "(chemical) element"
1224-643: A few decay products, to have been differentiated from other elements. Most recently, the synthesis of element 118 (since named oganesson ) was reported in October 2006, and the synthesis of element 117 ( tennessine ) was reported in April 2010. Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium , atomic number 43; promethium , number 61; astatine , number 85; francium , number 87; neptunium , number 93; and plutonium , number 94. These 94 elements have been detected in
1360-525: A few elements, such as silver and gold , are found uncombined as relatively pure native element minerals . Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is mostly a mixture of molecular nitrogen and oxygen , though it does contain compounds including carbon dioxide and water , as well as atomic argon , a noble gas which is chemically inert and therefore does not undergo chemical reactions. The history of
1496-421: A few millikelvins. It is possible to produce exotic helium isotopes , which rapidly decay into other substances. The shortest-lived heavy helium isotope is the unbound helium-10 with a half-life of 2.6(4) × 10 s . Helium-6 decays by emitting a beta particle and has a half-life of 0.8 second. Helium-7 and helium-8 are created in certain nuclear reactions . Helium-6 and helium-8 are known to exhibit
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#17328589474901632-524: A gas-like index of refraction of 1.026 which makes its surface so hard to see that floats of Styrofoam are often used to show where the surface is. This colorless liquid has a very low viscosity and a density of 0.145–0.125 g/mL (between about 0 and 4 K), which is only one-fourth the value expected from classical physics . Quantum mechanics is needed to explain this property and thus both states of liquid helium (helium I and helium II) are called quantum fluids , meaning they display atomic properties on
1768-472: A helium-oxygen bond could be stable. Two new molecular species, predicted using theory, CsFHeO and N(CH 3 ) 4 FHeO, are derivatives of a metastable FHeO anion first theorized in 2005 by a group from Taiwan. Helium atoms have been inserted into the hollow carbon cage molecules (the fullerenes ) by heating under high pressure. The endohedral fullerene molecules formed are stable at high temperatures. When chemical derivatives of these fullerenes are formed,
1904-410: A lower boiling point, can achieve about 0.2 kelvin in a helium-3 refrigerator . Equal mixtures of liquid He and He below 0.8 K separate into two immiscible phases due to their dissimilarity (they follow different quantum statistics : helium-4 atoms are bosons while helium-3 atoms are fermions ). Dilution refrigerators use this immiscibility to achieve temperatures of
2040-434: A macroscopic scale. This may be an effect of its boiling point being so close to absolute zero, preventing random molecular motion ( thermal energy ) from masking the atomic properties. Liquid helium below its lambda point (called helium II ) exhibits very unusual characteristics. Due to its high thermal conductivity , when it boils, it does not bubble but rather evaporates directly from its surface. Helium-3 also has
2176-459: 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 32 to 50 K at 1 atmosphere) does it cool upon free expansion. Once precooled below this temperature, helium can be liquefied through expansion cooling. Most extraterrestrial helium is plasma in stars, with properties quite different from those of atomic helium. In
2312-427: A new form of hydrogen with half-integer transition levels. In 1912, Alfred Fowler managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin. Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He . Fowler
2448-516: A phenomenon now called superfluidity . This phenomenon is related to Bose–Einstein condensation . In 1972, the same phenomenon was observed in helium-3 , but at temperatures much closer 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-3 fermions to make bosons , in analogy to Cooper pairs of electrons producing superconductivity . In 1961, Vignos and Fairbank reported
2584-591: A plasma, helium's electrons are not bound to its nucleus, 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, the particles interact with the Earth's magnetosphere , giving rise to Birkeland currents and the aurora . Helium liquifies when cooled below 4.2 K at atmospheric pressure. Unlike any other element, however, helium remains liquid down to
2720-500: A pressure of 1 bar and a given temperature (typically at 298.15K). However, for phosphorus, the reference state is white phosphorus even though it is not the most stable allotrope, and the reference state for carbon is graphite, because the structure of graphite is more stable than that of the other allotropes. In thermochemistry , an element is defined to have an enthalpy of formation of zero in its reference state. Several kinds of descriptive categorizations can be applied broadly to
2856-483: A pressure of one atmosphere, are commonly used in characterizing the various elements. While known for most elements, either or both of these measurements is still undetermined for some of the radioactive elements available in only tiny quantities. Since helium remains a liquid even at absolute zero at atmospheric pressure, it has only a boiling point, and not a melting point, in conventional presentations. The density at selected standard temperature and pressure (STP)
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#17328589474902992-441: A pressurizing and purge gas, as a protective atmosphere for arc welding , and in processes such as growing crystals to make silicon wafers —account for half of the gas produced. A small but well-known use is as a lifting gas in balloons and airships . As with any gas whose density differs from that of air, inhaling a small volume of helium temporarily changes the timbre and quality of the human voice . In scientific research,
3128-430: A rate three times that of air and around 65% that of hydrogen. Helium is the least water- soluble monatomic gas, and one of the least water-soluble of any gas ( CF 4 , SF 6 , and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 , respectively, versus helium's 0.70797 x 2 /10 ), and helium's index of refraction is closer to unity than that of any other gas. Helium has
3264-478: A reconsideration of the Pickering–Fowler series as central evidence in support of his model of the atom . This series is named for Edward Charles Pickering , who in 1896 published observations of previously unknown lines in the spectrum of the star ζ Puppis (these are now known to occur with Wolf–Rayet and other hot stars). Pickering attributed the observation (lines at 4551, 5411, and 10123 Å ) to
3400-445: A result of this creeping behavior and helium II's ability to leak rapidly through tiny openings, it is very difficult to confine. 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. Waves propagating across a Rollin film are governed by the same equation as gravity waves in shallow water, but rather than gravity,
3536-671: A risk of 'embolic shower' from micro clots that have formed on the surface of the balloon, and can lead to peripheral thrombosis, myocardial ischemia , hemodynamic decompensation, and late pseudoaneurysm . The first publication of intra-aortic balloon counter-pulsation appeared in the American Heart Journal of May 1962; 63: 669-675 by S. Moulopoulos, S. Topaz and W. Kolff. The device and the balloons were then developed for commercial use between 1967 and 1969 heart surgery by William Rassman, M.D. at Cornell Medical Center and were manufactured by Datascope Corporation in 1969. The system
3672-456: A small group, (the metalloids ), having intermediate properties and often behaving as semiconductors . A more refined classification is often shown in colored presentations of the periodic table. This system restricts the terms "metal" and "nonmetal" to only certain of the more broadly defined metals and nonmetals, adding additional terms for certain sets of the more broadly viewed metals and nonmetals. The version of this classification used in
3808-463: A surface extends past the level of helium II, the helium II moves along the surface, 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, Bernard V. Rollin . As
3944-449: A temperature of absolute zero . This is a direct effect of quantum mechanics: specifically, the zero point energy of the system is too high to allow freezing. Pressures above about 25 atmospheres are required to freeze it. There are two liquid phases: Helium I is a conventional liquid, and Helium II, which occurs at a lower temperature, is a superfluid . Below its boiling point of 4.22 K (−268.93 °C; −452.07 °F) and above
4080-474: A whole number. For example, the relative atomic mass of chlorine is 35.453 u, which differs greatly from a whole number as it is an average of about 76% chlorine-35 and 24% chlorine-37. Whenever a relative atomic mass value differs by more than ~1% from a whole number, it is due to this averaging effect, as significant amounts of more than one isotope are naturally present in a sample of that element. Chemists and nuclear scientists have different definitions of
4216-464: A γ phase, which is body-centered cubic (bcc). There are nine known isotopes of helium of which two, helium-3 and helium-4 , are stable . In the Earth's atmosphere, one atom is He for every million that are He . Unlike most elements, helium's isotopic abundance varies greatly by origin, due to the different formation processes. The most common isotope, helium-4, is produced on Earth by alpha decay of heavier radioactive elements;
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4352-403: Is 0.187 ± 0.009 g/cm . At higher temperatures, helium will solidify with sufficient pressure. At room temperature, this requires about 114,000 atm. Helium-4 and helium-3 both form several crystalline solid phases, all requiring at least 25 bar. They both form an α phase, which has a hexagonal close-packed (hcp) crystal structure, a β phase, which is face-centered cubic (fcc), and
4488-404: Is 10 (for tin , element 50). The mass number of an element, A , is the number of nucleons (protons and neutrons) in the atomic nucleus. Different isotopes of a given element are distinguished by their mass number, which is written as a superscript on the left hand side of the chemical symbol (e.g., U). The mass number is always an integer and has units of "nucleons". Thus, magnesium-24 (24
4624-434: Is a chemical element ; it has symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert , monatomic gas and the first in the noble gas group in the periodic table . Its boiling point is the lowest among all the elements , and it does not have a melting point at standard pressures. It is the second-lightest and second most abundant element in the observable universe , after hydrogen . It
4760-606: Is a mixture of C (about 98.9%), C (about 1.1%) and about 1 atom per trillion of C. Most (54 of 94) naturally occurring elements have more than one stable isotope. Except for the isotopes of hydrogen (which differ greatly from each other in relative mass—enough to cause chemical effects), the isotopes of a given element are chemically nearly indistinguishable. All elements have radioactive isotopes (radioisotopes); most of these radioisotopes do not occur naturally. Radioisotopes typically decay into other elements via alpha decay , beta decay , or inverse beta decay ; some isotopes of
4896-406: Is a dimensionless number equal to the atomic mass divided by the atomic mass constant , which equals 1 Da. In general, the mass number of a given nuclide differs in value slightly from its relative atomic mass, since the mass of each proton and neutron is not exactly 1 Da; since the electrons contribute a lesser share to the atomic mass as neutron number exceeds proton number; and because of
5032-407: Is a non-renewable resource because once released into the atmosphere, it promptly escapes into space . Its supply is thought to be rapidly diminishing. However, some studies suggest that helium produced deep in the Earth by radioactive decay can collect in natural gas reserves in larger-than-expected quantities, in some cases having been released by volcanic activity. The first evidence of helium
5168-812: Is an ongoing area of scientific study. The lightest elements are hydrogen and helium , both created by Big Bang nucleosynthesis in the first 20 minutes of the universe in a ratio of around 3:1 by mass (or 12:1 by number of atoms), along with tiny traces of the next two elements, lithium and beryllium . Almost all other elements found in nature were made by various natural methods of nucleosynthesis . On Earth, small amounts of new atoms are naturally produced in nucleogenic reactions, or in cosmogenic processes, such as cosmic ray spallation . New atoms are also naturally produced on Earth as radiogenic daughter isotopes of ongoing radioactive decay processes such as alpha decay , beta decay , spontaneous fission , cluster decay , and other rarer modes of decay. Of
5304-460: Is based on a Latin or other traditional word, for example adopting "gold" rather than "aurum" as the name for the 79th element (Au). IUPAC prefers the British spellings " aluminium " and "caesium" over the U.S. spellings "aluminum" and "cesium", and the U.S. "sulfur" over British "sulphur". However, elements that are practical to sell in bulk in many countries often still have locally used national names, and countries whose national language does not use
5440-399: 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
5576-447: Is created by the natural radioactive decay of heavy radioactive elements ( thorium and uranium , although there are other examples), as the alpha particles emitted by such decays consist of helium-4 nuclei . This radiogenic helium is trapped with natural gas in concentrations as great as 7% by volume, from which it is extracted commercially by a low-temperature separation process called fractional distillation . Terrestrial helium
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5712-411: Is little turbulent flow, so the balloon can inflate quickly and deflate slowly. It is also relatively benign and eliminated quickly if there is a leak or rupture in the balloon. The following situations may benefit from this device. The following conditions will always exclude patients for treatment: The following conditions make IABP therapy inadvisable except under pressing circumstances: IABP has
5848-413: Is no exception. Thus, numerical mathematical methods are required, even to solve the system of one nucleus and two electrons. Such computational chemistry methods have been used to create a quantum mechanical picture of helium electron binding which is accurate to within < 2% of the correct value, in a few computational steps. Such models show that each electron in helium partly screens the nucleus from
5984-516: Is often jointly credited with detecting the element, along with Norman Lockyer . Janssen recorded the helium spectral line during the solar eclipse of 1868, while Lockyer observed it from Britain. However, only Lockyer proposed that the line was due to a new element, which he named after the Sun. The formal discovery of the element was made in 1895 by chemists Sir William Ramsay , Per Teodor Cleve , and Nils Abraham Langlet , who found helium emanating from
6120-436: Is often used in characterizing the elements. Density is often expressed in grams per cubic centimetre (g/cm ). Since several elements are gases at commonly encountered temperatures, their densities are usually stated for their gaseous forms; when liquefied or solidified, the gaseous elements have densities similar to those of the other elements. When an element has allotropes with different densities, one representative allotrope
6256-527: Is present at about 24% of the total elemental mass, which is more than 12 times the mass of all the heavier elements combined. Its abundance is similar to this in both the Sun and Jupiter , because of the very high nuclear binding energy (per nucleon ) of helium-4 , with respect to the next three elements after helium. This helium-4 binding energy also accounts for why it is a product of both nuclear fusion and radioactive decay . The most common isotope of helium in
6392-474: Is produced in fusion reactions from hydrogen, though its estimated abundance in the universe is about 10 relative to helium-4. The unusual stability of the helium-4 nucleus is also important cosmologically : it explains the fact that in the first few minutes after the Big Bang , as the "soup" of free protons and neutrons which had initially been created in about 6:1 ratio cooled to the point that nuclear binding
6528-520: Is subjected to a glow discharge , to electron bombardment, or reduced to plasma by other means. The molecular compounds HeNe, HgHe 10 , and WHe 2 , and the molecular ions He 2 , He 2 , HeH , and HeD have been created this way. HeH is also stable in its ground state but is extremely reactive—it is the strongest Brønsted acid known, and therefore can exist only in isolation, as it will protonate any molecule or counteranion it contacts. This technique has also produced
6664-426: Is the mass number) is an atom with 24 nucleons (12 protons and 12 neutrons). Whereas the mass number simply counts the total number of neutrons and protons and is thus an integer, the atomic mass of a particular isotope (or "nuclide") of the element is the mass of a single atom of that isotope, and is typically expressed in daltons (symbol: Da), or universal atomic mass units (symbol: u). Its relative atomic mass
6800-466: Is the second least reactive noble gas after neon , and thus the second least reactive of all elements. It is chemically inert and monatomic in all standard conditions. Because of helium's relatively low molar (atomic) mass, its thermal conductivity , specific heat , and sound speed in the gas phase are all greater than any other gas except hydrogen . For these reasons and the small size of helium monatomic molecules, helium diffuses through solids at
6936-416: Is thus energetically extremely stable for all these particles and has astrophysical implications. Namely, adding another particle – proton, neutron, or alpha particle – would consume rather than release energy; all systems with mass number 5, as well as beryllium-8 (comprising two alpha particles), are unbound. For example, the stability and low energy of the electron cloud state in helium accounts for
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#17328589474907072-532: Is typically selected in summary presentations, while densities for each allotrope can be stated where more detail is provided. For example, the three familiar allotropes of carbon ( amorphous carbon , graphite , and diamond ) have densities of 1.8–2.1, 2.267, and 3.515 g/cm , respectively. The elements studied to date as solid samples have eight kinds of crystal structures : cubic , body-centered cubic , face-centered cubic, hexagonal , monoclinic , orthorhombic , rhombohedral , and tetragonal . For some of
7208-417: Is used in two different but closely related meanings: it can mean a chemical substance consisting of a single kind of atoms, or it can mean that kind of atoms as a component of various chemical substances. For example, molecules of water (H 2 O) contain atoms of hydrogen (H) and oxygen (O), so water can be said as a compound consisting of the elements hydrogen (H) and oxygen (O) even though it does not contain
7344-429: Is very strong; fullerenes , which have nearly spherical shapes; and carbon nanotubes , which are tubes with a hexagonal structure (even these may differ from each other in electrical properties). The ability of an element to exist in one of many structural forms is known as 'allotropy'. The reference state of an element is defined by convention, usually as the thermodynamically most stable allotrope and physical state at
7480-585: Is widely used. For example, the French chemical terminology distinguishes élément chimique (kind of atoms) and corps simple (chemical substance consisting of a single kind of atoms); the Russian chemical terminology distinguishes химический элемент and простое вещество . Almost all baryonic matter in the universe is composed of elements (among rare exceptions are neutron stars ). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds . Only
7616-402: The 2017 Qatar diplomatic crisis severely affected helium production there. 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages. Nasdaq reported (2015) that for Air Products , an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints. In
7752-480: The International Union of Pure and Applied Chemistry (IUPAC) had recognized a total of 118 elements. The first 94 occur naturally on Earth , and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements (radioelements) which decay quickly, nearly all elements are available industrially in varying amounts. The discovery and synthesis of further new elements
7888-625: The Latin alphabet are likely to use the IUPAC element names. According to IUPAC, element names are not proper nouns; therefore, the full name of an element is not capitalized in English, even if derived from a proper noun , as in californium and einsteinium . Isotope names are also uncapitalized if written out, e.g., carbon-12 or uranium-235 . Chemical element symbols (such as Cf for californium and Es for einsteinium), are always capitalized (see below). In
8024-558: The Naval Aircraft Factory -built USS Shenandoah , flew in September 1923. 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. During World War II, the demand increased for helium for lifting gas and for shielded arc welding . The helium mass spectrometer
8160-624: The beta decay of tritium . Rocks from the Earth's crust have isotope ratios varying by as much as a factor of ten, and these ratios can be used to investigate the origin of rocks and the composition of the Earth's mantle . He is much more abundant in stars as a product of nuclear fusion. Thus in the interstellar medium , the proportion of He to He is about 100 times higher than on Earth. Extraplanetary material, such as lunar and asteroid regolith , have trace amounts of helium-3 from being bombarded by solar winds . The Moon 's surface contains helium-3 at concentrations on
8296-423: The kinetic isotope effect is significant). Thus, all carbon isotopes have nearly identical chemical properties because they all have six electrons, even though they may have 6 to 8 neutrons. That is why atomic number, rather than mass number or atomic weight , is considered the identifying characteristic of an element. The symbol for atomic number is Z . Isotopes are atoms of the same element (that is, with
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#17328589474908432-413: The lambda point of 2.1768 K (−270.9732 °C; −455.7518 °F), the isotope helium-4 exists in a normal colorless liquid state, called helium I . Like other cryogenic liquids, helium I boils when it is heated and contracts when its temperature is lowered. Below the lambda point, however, helium does not boil, and it expands as the temperature is lowered further. Helium I has
8568-405: The nuclear binding energy and electron binding energy. For example, the atomic mass of chlorine-35 to five significant digits is 34.969 Da and that of chlorine-37 is 36.966 Da. However, the relative atomic mass of each isotope is quite close to its mass number (always within 1%). The only isotope whose atomic mass is exactly a natural number is C, which has a mass of 12 Da; because
8704-399: The renal artery and subsequent kidney failure . Other possible complications are cerebral embolism during insertion, infection, dissection of the aorta or iliac artery , perforation of the artery and bleeding in the mediastinum . Mechanical failure of the balloon itself is also a risk which entails vascular surgery to remove under that circumstance. After balloon removal there is also
8840-616: The uranium ore cleveite , which is now not regarded as a separate mineral species, but as a variety of uraninite . In 1903, large reserves of helium were found in natural gas fields in parts of the United States, by far the largest supplier of the gas today. Liquid helium is used in cryogenics (its largest single use, consuming about a quarter of production), and in the cooling of superconducting magnets , with its main commercial application in MRI scanners. Helium's other industrial uses—as
8976-638: The 94 naturally occurring elements, those with atomic numbers 1 through 82 each have at least one stable isotope (except for technetium , element 43 and promethium , element 61, which have no stable isotopes). Isotopes considered stable are those for which no radioactive decay has yet been observed. Elements with atomic numbers 83 through 94 are unstable to the point that radioactive decay of all isotopes can be detected. Some of these elements, notably bismuth (atomic number 83), thorium (atomic number 90), and uranium (atomic number 92), have one or more isotopes with half-lives long enough to survive as remnants of
9112-462: The Earth, and for carbon-based or other life) have thus been created since the Big Bang in stars which were hot enough to fuse helium itself. All elements other than hydrogen and helium today account for only 2% of the mass of atomic matter in the universe. Helium-4, by contrast, comprises about 24% of the mass of the universe's ordinary matter—nearly all the ordinary matter that is not hydrogen. Helium
9248-487: The French, Italians, Greeks, Portuguese and Poles prefer "azote/azot/azoto" (from roots meaning "no life") for "nitrogen". For purposes of international communication and trade, the official names of the chemical elements both ancient and more recently recognized are decided by the International Union of Pure and Applied Chemistry (IUPAC), which has decided on a sort of international English language, drawing on traditional English names even when an element's chemical symbol
9384-460: The Interior to empty the reserve, with sales starting by 2005. Helium produced between 1930 and 1945 was about 98.3% 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 99.95% helium were available. For many years, the United States produced more than 90% of commercially usable helium in
9520-605: 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 (684 km) pipeline from Bushton, Kansas , to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture
9656-440: The alpha particles that emerge are fully ionized helium-4 nuclei. Helium-4 is an unusually stable nucleus because its nucleons are arranged into complete shells . It was also formed in enormous quantities during Big Bang nucleosynthesis . Helium-3 is present on Earth only in trace amounts. Most of it has been present since Earth's formation, though some falls to Earth trapped in cosmic dust . Trace amounts are also produced by
9792-487: The atomic masses of the elements (their atomic weights or atomic masses) do not always increase monotonically with their atomic numbers. The naming of various substances now known as elements precedes the atomic theory of matter, as names were given locally by various cultures to various minerals, metals, compounds, alloys, mixtures, and other materials, though at the time it was not known which chemicals were elements and which compounds. As they were identified as elements,
9928-412: The behavior of the two fluid phases of helium-4 (helium I and helium II) is important to researchers studying quantum mechanics (in particular the property of superfluidity ) and to those looking at the phenomena, such as superconductivity , produced in matter near absolute zero . On Earth, it is relatively rare—5.2 ppm by volume in the atmosphere . Most terrestrial helium present today
10064-413: The chemical substances (di)hydrogen (H 2 ) and (di)oxygen (O 2 ), as H 2 O molecules are different from H 2 and O 2 molecules. For the meaning "chemical substance consisting of a single kind of atoms", the terms "elementary substance" and "simple substance" have been suggested, but they have not gained much acceptance in English chemical literature, whereas in some other languages their equivalent
10200-408: The dalton is defined as 1/12 of the mass of a free neutral carbon-12 atom in the ground state. The standard atomic weight (commonly called "atomic weight") of an element is the average of the atomic masses of all the chemical element's isotopes as found in a particular environment, weighted by isotopic abundance, relative to the atomic mass unit. This number may be a fraction that is not close to
10336-416: The discovery and use of elements began with early human societies that discovered native minerals like carbon , sulfur , copper and gold (though the modern concept of an element was not yet understood). Attempts to classify materials such as these resulted in the concepts of classical elements , alchemy , and similar theories throughout history. Much of the modern understanding of elements developed from
10472-446: The element's chemical inertness, and also the lack of interaction of helium atoms with each other, producing the lowest melting and boiling points of all the elements. In a similar way, the particular energetic stability of the helium-4 nucleus, produced by similar effects, accounts for the ease of helium-4 production in atomic reactions that involve either heavy-particle emission or fusion. Some stable helium-3 (two protons and one neutron)
10608-406: The elements are available by name, atomic number, density, melting point, boiling point and chemical symbol , as well as ionization energy . The nuclides of stable and radioactive elements are also available as a list of nuclides , sorted by length of half-life for those that are unstable. One of the most convenient, and certainly the most traditional presentation of the elements, is in the form of
10744-470: The elements are often summarized using the periodic table, which powerfully and elegantly organizes the elements by increasing atomic number into rows ( "periods" ) in which the columns ( "groups" ) share recurring ("periodic") physical and chemical properties. The table contains 118 confirmed elements as of 2021. Although earlier precursors to this presentation exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended
10880-480: The elements can be uniquely sequenced by atomic number, conventionally from lowest to highest (as in a periodic table), sets of elements are sometimes specified by such notation as "through", "beyond", or "from ... through", as in "through iron", "beyond uranium", or "from lanthanum through lutetium". The terms "light" and "heavy" are sometimes also used informally to indicate relative atomic numbers (not densities), as in "lighter than carbon" or "heavier than lead", though
11016-413: The elements without any stable isotopes are technetium (atomic number 43), promethium (atomic number 61), and all observed elements with atomic number greater than 82. Of the 80 elements with at least one stable isotope, 26 have only one stable isotope. The mean number of stable isotopes for the 80 stable elements is 3.1 stable isotopes per element. The largest number of stable isotopes for a single element
11152-474: The elements, including consideration of their general physical and chemical properties, their states of matter under familiar conditions, their melting and boiling points, their densities, their crystal structures as solids, and their origins. Several terms are commonly used to characterize the general physical and chemical properties of the chemical elements. A first distinction is between metals , which readily conduct electricity , nonmetals , which do not, and
11288-505: The existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K. After an oil drilling operation in 1903 in Dexter, Kansas produced a gas geyser 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
11424-517: The existence of this new element. The ending "-ium" is unusual, as it normally applies only to metallic elements; probably Lockyer, being an astronomer, was unaware of the chemical conventions. In 1881, Italian physicist Luigi Palmieri detected helium on Earth for the first time through its D 3 spectral line, when he analyzed a material that had been sublimated during a recent eruption of Mount Vesuvius . On March 26, 1895, Scottish chemist Sir William Ramsay isolated helium on Earth by treating
11560-492: The existing names for anciently known elements (e.g., gold, mercury, iron) were kept in most countries. National differences emerged over the element names either for convenience, linguistic niceties, or nationalism. For example, German speakers use "Wasserstoff" (water substance) for "hydrogen", "Sauerstoff" (acid substance) for "oxygen" and "Stickstoff" (smothering substance) for "nitrogen"; English and some other languages use "sodium" for "natrium", and "potassium" for "kalium"; and
11696-630: The explosive stellar nucleosynthesis that produced the heavy metals before the formation of our Solar System . At over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope, and is almost always considered on par with the 80 stable elements. The heaviest elements (those beyond plutonium, element 94) undergo radioactive decay with half-lives so short that they are not found in nature and must be synthesized . There are now 118 known elements. In this context, "known" means observed well enough, even from just
11832-451: The few minutes after the Big Bang, before the early expanding universe cooled to the temperature and pressure point where helium fusion to carbon was no longer possible. This left the early universe with a very similar ratio of hydrogen/helium as is observed today (3 parts hydrogen to 1 part helium-4 by mass), with nearly all the neutrons in the universe trapped in helium-4. All heavier elements (including those necessary for rocky planets like
11968-529: The formation of Earth, they are certain to have completely decayed, and if present in novae, are in quantities too small to have been noted. Technetium was the first purportedly non-naturally occurring element synthesized, in 1937, though trace amounts of technetium have since been found in nature (and also the element may have been discovered naturally in 1925). This pattern of artificial production and later natural discovery has been repeated with several other radioactive naturally occurring rare elements. List of
12104-431: The half-lives predicted for the observationally stable lead isotopes range from 10 to 10 years. Elements with atomic numbers 43, 61, and 83 through 94 are unstable enough that their radioactive decay can be detected. Three of these elements, bismuth (element 83), thorium (90), and uranium (92) have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced
12240-420: The heat. Helium II has no such valence band but nevertheless conducts heat well. The flow of heat is governed by equations that are similar to the wave equation used to characterize sound propagation in air. When heat is introduced, it moves at 20 meters per second at 1.8 K through helium II as waves in a phenomenon known as second sound . Helium II also exhibits a creeping effect. When
12376-399: The heaviest elements also undergo spontaneous fission . Isotopes that are not radioactive, are termed "stable" isotopes. All known stable isotopes occur naturally (see primordial nuclide ). The many radioisotopes that are not found in nature have been characterized after being artificially produced. Certain elements have no stable isotopes and are composed only of radioisotopes: specifically
12512-543: The heavy elements before the formation of the Solar System. For example, at over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope. The last 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus are not known to occur in nature at all. 1 The properties of
12648-567: The helium stays inside. If helium-3 is used, it can be readily observed by helium nuclear magnetic resonance spectroscopy . Many fullerenes containing helium-3 have been reported. Although the helium atoms are not attached by covalent or ionic bonds, these substances have distinct properties and a definite composition, like all stoichiometric chemical compounds. Under high pressures helium can form compounds with various other elements. Helium-nitrogen clathrate (He(N 2 ) 11 ) crystals have been grown at room temperature at pressures ca. 10 GPa in
12784-400: 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. With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium. This showed that despite its overall rarity on Earth, helium
12920-535: The left femoral artery . Pumping was performed for approximately 6 hours. Shock reversed and the patient was discharged. The size of the original balloon was 15 French but eventually 9 and 8 French balloons were developed. A second operation removed the balloon. Since 1979 the placement of the balloon has been modified using the Seldinger technique. Helium Helium (from Greek : ἥλιος , romanized : helios , lit. 'sun')
13056-429: The lines to nitrogen . His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science. 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 spectrum of the new gas inside. In 1908, helium
13192-427: The mineral cleveite (a variety of uraninite with at least 10% rare-earth elements ) with mineral acids . Ramsay was looking for argon but, after separating nitrogen and oxygen from the gas, liberated by sulfuric acid , he noticed a bright yellow line that matched the D 3 line observed in the spectrum of the Sun. These samples were identified as helium by Lockyer and British physicist William Crookes . It
13328-497: The neutral molecule He 2 , which has a large number of band systems , and HgHe, which is apparently held together only by polarization forces. Van der Waals compounds of helium can also be formed with cryogenic helium gas and atoms of some other substance, such as LiHe and He 2 . Theoretically, other true compounds may be possible, such as helium fluorohydride (HHeF), which would be analogous to HArF , discovered in 2000. Calculations show that two new compounds containing
13464-467: The order of 10 ppb , much higher than the approximately 5 ppt found in the Earth's atmosphere. A number of people, starting with Gerald Kulcinski in 1986, have proposed to explore the Moon, mine lunar regolith, and use the helium-3 for fusion . Liquid helium-4 can be cooled to about 1 K (−272.15 °C; −457.87 °F) using evaporative cooling in a 1-K pot . Similar cooling of helium-3, which has
13600-475: The other, so that the effective nuclear charge Z eff which each electron sees is about 1.69 units, not the 2 charges of a classic "bare" helium nucleus. The nucleus of the helium-4 atom is identical with an alpha particle . High-energy electron-scattering experiments show its charge to decrease exponentially from a maximum at a central point, exactly as does the charge density of helium's own electron cloud . This symmetry reflects similar underlying physics:
13736-402: The pair of neutrons and the pair of protons in helium's nucleus obey the same quantum mechanical rules as do helium's pair of electrons (although the nuclear particles are subject to a different nuclear binding potential), so that all these fermions fully occupy 1s orbitals in pairs, none of them possessing orbital angular momentum, and each cancelling the other's intrinsic spin. This arrangement
13872-418: The periodic table, which groups together elements with similar chemical properties (and usually also similar electronic structures). The atomic number of an element is equal to the number of protons in each atom, and defines the element. For example, all carbon atoms contain 6 protons in their atomic nucleus ; so the atomic number of carbon is 6. Carbon atoms may have different numbers of neutrons; atoms of
14008-426: The periodic tables presented here includes: actinides , alkali metals , alkaline earth metals , halogens , lanthanides , transition metals , post-transition metals , metalloids , reactive nonmetals , and noble gases . In this system, the alkali metals, alkaline earth metals, and transition metals, as well as the lanthanides and the actinides, are special groups of the metals viewed in a broader sense. Similarly,
14144-472: The perspective of quantum mechanics , helium is the second simplest atom to model, following the hydrogen atom . Helium is composed of two electrons in atomic orbitals surrounding a nucleus containing two protons and (usually) two neutrons. As in Newtonian mechanics, no system that consists of more than two particles can be solved with an exact analytical mathematical approach (see 3-body problem ) and helium
14280-420: 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 mechanism. Most materials that conduct heat well have a valence band of free electrons which serve to transfer
14416-510: The prohibitive cost of the gas, German Zeppelins were forced to use hydrogen as lifting gas, which would gain infamy in the Hindenburg disaster . The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of liquid helium as a coolant to create oxygen/hydrogen rocket fuel (among other uses) during the Space Race and Cold War . Helium use in
14552-412: The pure element to exist in multiple chemical structures ( spatial arrangements of atoms ), known as allotropes , which differ in their properties. For example, carbon can be found as diamond , which has a tetrahedral structure around each carbon atom; graphite , which has layers of carbon atoms with a hexagonal structure stacked on top of each other; graphene , which is a single layer of graphite that
14688-772: The reactive nonmetals and the noble gases are nonmetals viewed in the broader sense. In some presentations, the halogens are not distinguished, with astatine identified as a metalloid and the others identified as nonmetals. Another commonly used basic distinction among the elements is their state of matter (phase), whether solid , liquid , or gas , at standard temperature and pressure (STP). Most elements are solids at STP, while several are gases. Only bromine and mercury are liquid at 0 degrees Celsius (32 degrees Fahrenheit) and 1 atmosphere pressure; caesium and gallium are solid at that temperature, but melt at 28.4°C (83.2°F) and 29.8°C (85.6°F), respectively. Melting and boiling points , typically expressed in degrees Celsius at
14824-919: The remaining 11 elements have half lives too short for them to have been present at the beginning of the Solar System, and are therefore considered transient elements. Of these 11 transient elements, five ( polonium , radon , radium , actinium , and protactinium ) are relatively common decay products of thorium and uranium . The remaining six transient elements (technetium, promethium, astatine, francium , neptunium , and plutonium ) occur only rarely, as products of rare decay modes or nuclear reaction processes involving uranium or other heavy elements. Elements with atomic numbers 1 through 82, except 43 (technetium) and 61 (promethium), each have at least one isotope for which no radioactive decay has been observed. Observationally stable isotopes of some elements (such as tungsten and lead ), however, are predicted to be slightly radioactive with very long half-lives: for example,
14960-601: The reserve to continue to sell the gas. Other large reserves were in the Hugoton in Kansas , United States, and nearby gas fields of Kansas and the panhandles of Texas and Oklahoma . New helium plants were scheduled to open in 2012 in Qatar , Russia, and the US state of Wyoming , but they were not expected to ease the shortage. In 2013, Qatar started up the world's largest helium unit, although
15096-422: The restoring force is the van der Waals force . These waves are known as third sound . Helium remains liquid down to absolute zero at atmospheric pressure, but it freezes at high pressure. Solid helium requires a temperature of 1–1.5 K (about −272 °C or −457 °F) at about 25 bar (2.5 MPa) of pressure. It is often hard to distinguish solid from liquid helium since the refractive index of
15232-624: The same element can have different numbers of neutrons in their nuclei, known as isotopes of the element. Two or more atoms can combine to form molecules . Some elements are formed from molecules of identical atoms , e. g. atoms of hydrogen (H) form diatomic molecules (H 2 ). Chemical compounds are substances made of atoms of different elements; they can have molecular or non-molecular structure. Mixtures are materials containing different chemical substances; that means (in case of molecular substances) that they contain different types of molecules. Atoms of one element can be transformed into atoms of
15368-495: The same element having different numbers of neutrons are known as isotopes of the element. The number of protons in the nucleus also determines its electric charge , which in turn determines the number of electrons of the atom in its non-ionized state. The electrons are placed into atomic orbitals that determine the atom's chemical properties . The number of neutrons in a nucleus usually has very little effect on an element's chemical properties; except for hydrogen (for which
15504-404: The same number of protons in their nucleus), but having different numbers of neutrons . Thus, for example, there are three main isotopes of carbon. All carbon atoms have 6 protons, but they can have either 6, 7, or 8 neutrons. Since the mass numbers of these are 12, 13 and 14 respectively, said three isotopes are known as carbon-12 , carbon-13 , and carbon-14 ( C, C, and C). Natural carbon
15640-457: The second half of the 20th century, physics laboratories became able to produce elements with half-lives too short for an appreciable amount of them to exist at any time. These are also named by IUPAC, which generally adopts the name chosen by the discoverer. This practice can lead to the controversial question of which research group actually discovered an element, a question that delayed the naming of elements with atomic number of 104 and higher for
15776-547: The second leading producer of helium. Through this time, both helium consumption and the costs of producing helium increased. From 2002 to 2007 helium prices doubled. As of 2012 , the United States National Helium Reserve accounted for 30 percent of the world's helium. The reserve was expected to run out of helium in 2018. Despite that, a proposed bill in the United States Senate would allow
15912-458: The solar spectrum, which he named the D 3 because it was near the known D 1 and D 2 Fraunhofer lines of sodium. He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer named the element with the Greek word for the Sun, ἥλιος ( helios ). It is sometimes said that English chemist Edward Frankland was also involved in the naming, but this is unlikely as he doubted
16048-496: The synthetically produced transuranic elements, available samples have been too small to determine crystal structures. Chemical elements may also be categorized by their origin on Earth, with the first 94 considered naturally occurring, while those with atomic numbers beyond 94 have only been produced artificially via human-made nuclear reactions. Of the 94 naturally occurring elements, 83 are considered primordial and either stable or weakly radioactive. The longest-lived isotopes of
16184-955: The table to illustrate recurring trends in the properties of the elements. The layout of the table has been refined and extended over time as new elements have been discovered and new theoretical models have been developed to explain chemical behavior. Use of the periodic table is now ubiquitous in chemistry, providing an extremely useful framework to classify, systematize and compare all the many different forms of chemical behavior. The table has also found wide application in physics , geology , biology , materials science , engineering , agriculture , medicine , nutrition , environmental health , and astronomy . Its principles are especially important in chemical engineering . The various chemical elements are formally identified by their unique atomic numbers, their accepted names, and their chemical symbols . The known elements have atomic numbers from 1 to 118, conventionally presented as Arabic numerals . Since
16320-450: The two phases are nearly the same. The solid has a sharp melting point and has a crystalline structure, but it is highly compressible ; applying pressure in a laboratory can decrease its volume by more than 30%. With a bulk modulus of about 27 MPa it is ~100 times more compressible than water. Solid helium has a density of 0.214 ± 0.006 g/cm at 1.15 K and 66 atm; the projected density at 0 K and 25 bar (2.5 MPa)
16456-615: The universe at large, in the spectra of stars and also supernovae, where short-lived radioactive elements are newly being made. The first 94 elements have been detected directly on Earth as primordial nuclides present from the formation of the Solar System , or as naturally occurring fission or transmutation products of uranium and thorium. The remaining 24 heavier elements, not found today either on Earth or in astronomical spectra, have been produced artificially: all are radioactive, with short half-lives; if any of these elements were present at
16592-461: The universe is helium-4, the vast majority of which was formed during the Big Bang . Large amounts of new helium are created by nuclear fusion of hydrogen in stars . Helium was first detected as an unknown, yellow spectral line signature in sunlight during a solar eclipse in 1868 by Georges Rayet , Captain C. T. Haig, Norman R. Pogson , and Lieutenant John Herschel, and was subsequently confirmed by French astronomer Jules Janssen . Janssen
16728-528: The work of Dmitri Mendeleev , a Russian chemist who published the first recognizable periodic table in 1869. This table organizes the elements by increasing atomic number into rows (" periods ") in which the columns (" groups ") share recurring ("periodic") physical and chemical properties . The periodic table summarizes various properties of the elements, allowing chemists to derive relationships between them and to make predictions about elements not yet discovered, and potential new compounds. By November 2016,
16864-669: The world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in Arzew , Algeria, producing 17 million cubic metres (600 million cubic feet) began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year. In 2004–2006, additional plants in Ras Laffan , Qatar , and Skikda , Algeria were built. Algeria quickly became
17000-520: 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 airships in time of war and commercial airships in peacetime. Because of the Helium Act of 1925 , which banned the export of scarce helium on which the US then had a production monopoly, together with
17136-409: Was available to make elements 3, 4 and 5. It is barely energetically favorable for helium to fuse into the next element with a lower energy per nucleon , carbon. However, due to the short lifetime of the intermediate beryllium-8, this process requires three helium nuclei striking each other nearly simultaneously (see triple-alpha process ). There was thus no time for significant carbon to be formed in
17272-553: Was concentrated in large quantities under the American Great Plains , available for extraction as a byproduct of natural gas . Following a suggestion by Sir Richard Threlfall , the United States Navy sponsored three small experimental helium 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 m (200,000 cu ft) of 92% helium
17408-500: Was first liquefied by Dutch physicist Heike Kamerlingh Onnes by cooling the gas to less than 5 K (−268.15 °C; −450.67 °F). He tried to solidify it by further reducing the temperature but failed, because helium does not solidify at atmospheric pressure. Onnes' student Willem Hendrik Keesom was eventually able to solidify 1 cm of helium in 1926 by applying additional external pressure. In 1913, Niels Bohr published his "trilogy" on atomic structure that included
17544-488: 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 . Helium was also isolated by 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
17680-690: Was initially skeptical but was ultimately convinced that Bohr was correct, and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium." Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory. In 1938, Russian physicist Pyotr Leonidovich Kapitsa discovered that helium-4 has almost no viscosity at temperatures near absolute zero ,
17816-582: Was injected and stored in the Cliffside gas field until needed, at which time it was further purified. By 1995, a billion cubic meters of the gas had been collected and the reserve was US$ 1.4 billion in debt, prompting the Congress of the United States in 1996 to discontinue the reserve. The resulting Helium Privatization Act of 1996 (Public Law 104–273) directed the United States Department of
17952-453: Was observed 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 Jules Janssen during a total solar eclipse in Guntur , India. This line was initially assumed to be sodium . On October 20 of the same year, English astronomer Norman Lockyer observed a yellow line in
18088-406: Was observed. Existing 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. In the fountain effect , a chamber
18224-522: Was possible, almost all first compound atomic nuclei to form were helium-4 nuclei. Owing to the relatively tight binding of helium-4 nuclei, its production consumed nearly all of the free neutrons in a few minutes, before they could beta-decay, and thus few neutrons were available to form heavier atoms such as lithium, beryllium, or boron. Helium-4 nuclear binding per nucleon is stronger than in any of these elements (see nucleogenesis and binding energy ) and thus, once helium had been formed, no energetic drive
18360-507: Was produced in the program even though less than a cubic meter of the gas had previously been obtained. Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's C-class blimp C-7, which flew its maiden voyage from Hampton Roads, Virginia , to Bolling Field in Washington, D.C., on December 1, 1921, nearly two years before the Navy's first rigid helium-filled airship,
18496-511: Was subsequently used clinically by Dr. David Bregman in 1976 at NewYork-Presbyterian Hospital in New York City . The first clinical implant was performed at Maimonides Medical Center , Brooklyn, N.Y. in June 1967 by Dr. Adrian Kantrowitz and Dr. Steven Phillips. The patient, a 48-year-old woman, was in cardiogenic shock and unresponsive to traditional therapy. An IABP was inserted by a cut down on
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