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114-510: Gallium is a chemical element ; it has the symbol Ga and atomic number 31. Discovered by the French chemist Paul-Émile Lecoq de Boisbaudran in 1875, gallium is in group 13 of the periodic table and is similar to the other metals of the group ( aluminium , indium , and thallium ). Elemental gallium is a relatively soft, silvery metal at standard temperature and pressure . In its liquid state, it becomes silvery white. If enough force

228-505: A by-product during the processing of the ores of other metals. Its main source material is bauxite , the chief ore of aluminium , but minor amounts are also extracted from sulfidic zinc ores ( sphalerite being the main host mineral). In the past, certain coals were an important source. During the processing of bauxite to alumina in the Bayer process , gallium accumulates in the sodium hydroxide liquor. From this it can be extracted by

342-471: A direct bandgap semiconductor in the 1960s ushered in the most important stage in the applications of gallium. In the late 1960s, the electronics industry started using gallium on a commercial scale to fabricate light emitting diodes, photovoltaics and semiconductors, while the metals industry used it to reduce the melting point of alloys . Gallium does not exist as a free element in the Earth's crust, and

456-620: A passive , protective oxide layer. At higher temperatures, however, it reacts with atmospheric oxygen to form gallium(III) oxide , Ga 2 O 3 . Reducing Ga 2 O 3 with elemental gallium in vacuum at 500 °C to 700 °C yields the dark brown gallium(I) oxide , Ga 2 O . Ga 2 O is a very strong reducing agent , capable of reducing H 2 SO 4 to H 2 S . It disproportionates at 800 °C back to gallium and Ga 2 O 3 . Gallium(III) sulfide , Ga 2 S 3 , has 3 possible crystal modifications. It can be made by

570-464: A phase transition ; specifically the melting / freezing point of a pure chemical element. However, the deepest cryogenic points are based exclusively on the vapor pressure /temperature relationship of helium and its isotopes whereas the remainder of its cold points (those less than room temperature) are based on triple points . Examples of other defining points are the triple point of equilibrium hydrogen ( 13.8033 K or −259.3467 °C ) and

684-711: A phosphor . Gallium also forms sulfides in lower oxidation states, such as gallium(II) sulfide and the green gallium(I) sulfide , the latter of which is produced from the former by heating to 1000 °C under a stream of nitrogen. The other binary chalcogenides, Ga 2 Se 3 and Ga 2 Te 3 , have the zincblende structure. They are all semiconductors but are easily hydrolysed and have limited utility. Gallium reacts with ammonia at 1050 °C to form gallium nitride , GaN. Gallium also forms binary compounds with phosphorus , arsenic , and antimony : gallium phosphide (GaP), gallium arsenide (GaAs), and gallium antimonide (GaSb). These compounds have

798-738: 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

912-587: A by-product is defined as that amount which is economically extractable from its host materials per year under current market conditions (i.e. technology and price). Reserves and resources are not relevant for by-products, since they cannot be extracted independently from the main-products. Recent estimates put the supply potential of gallium at a minimum of 2,100 t/yr from bauxite, 85 t/yr from sulfidic zinc ores, and potentially 590 t/yr from coal. These figures are significantly greater than current production (375 t in 2016). Thus, major future increases in

1026-496: 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

1140-477: 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"

1254-652: 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

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1368-529: 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

1482-404: A greater volatility than ZnCl 2 : all of these predictions turned out to be true. Gallium was discovered using spectroscopy by French chemist Paul Emile Lecoq de Boisbaudran in 1875 from its characteristic spectrum (two violet lines) in a sample of sphalerite . Later that year, Lecoq obtained the free metal by electrolysis of the hydroxide in potassium hydroxide solution. He named

1596-437: A person's hands at normal human body temperature of 37.0 °C (98.6 °F). Gallium is predominantly used in electronics . Gallium arsenide , the primary chemical compound of gallium in electronics, is used in microwave circuits, high-speed switching circuits, and infrared circuits. Semiconducting gallium nitride and indium gallium nitride produce blue and violet light-emitting diodes and diode lasers . Gallium

1710-500: 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

1824-483: 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)

1938-456: 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

2052-483: A value on the Fahrenheit scale (e.g. 211.953 °F). ITS-90 does not address the highly specialized equipment and procedures used for measuring temperatures extremely close to absolute zero. For instance, to measure temperatures in the nanokelvin range (billionths of a kelvin), scientists using optical lattice laser equipment to adiabatically cool atoms, turn off the entrapment lasers and simply measure how far

2166-477: A variety of methods. The most recent is the use of ion-exchange resin . Achievable extraction efficiencies critically depend on the original concentration in the feed bauxite. At a typical feed concentration of 50 ppm, about 15% of the contained gallium is extractable. The remainder reports to the red mud and aluminium hydroxide streams. Gallium is removed from the ion-exchange resin in solution. Electrolysis then gives gallium metal. For semiconductor use, it

2280-474: 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

2394-404: 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

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2508-606: 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

2622-422: Is a common starting reagent for the formation of organogallium compounds, such as in carbogallation reactions. Gallium trichloride reacts with lithium cyclopentadienide in diethyl ether to form the trigonal planar gallium cyclopentadienyl complex GaCp 3 . Gallium(I) forms complexes with arene ligands such as hexamethylbenzene . Because this ligand is quite bulky, the structure of the [Ga(η-C 6 Me 6 )]

2736-406: 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

2850-487: Is a halogen. They also react with alkyl halides to form carbocations and GaX 4 . When heated to a high temperature, gallium(III) halides react with elemental gallium to form the respective gallium(I) halides. For example, GaCl 3 reacts with Ga to form GaCl : At lower temperatures, the equilibrium shifts toward the left and GaCl disproportionates back to elemental gallium and GaCl 3 . GaCl can also be produced by reacting Ga with HCl at 950 °C;

2964-550: Is also used in the production of artificial gadolinium gallium garnet for jewelry. Gallium is considered a technology-critical element by the United States National Library of Medicine and Frontiers Media . Gallium has no known natural role in biology. Gallium(III) behaves in a similar manner to ferric salts in biological systems and has been used in some medical applications, including pharmaceuticals and radiopharmaceuticals . Elemental gallium

3078-405: Is an ionic compound strongly insoluble in water. However, it dissolves in hydrofluoric acid , in which it forms an adduct with water, GaF 3 ·3H 2 O . Attempting to dehydrate this adduct forms GaF 2 OH· n H 2 O . The adduct reacts with ammonia to form GaF 3 ·3NH 3 , which can then be heated to form anhydrous GaF 3 . Gallium trichloride is formed by

3192-812: 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

3306-562: Is applied, solid gallium may fracture conchoidally . Since its discovery in 1875, gallium has widely been used to make alloys with low melting points. It is also used in semiconductors , as a dopant in semiconductor substrates. The melting point of gallium (29.7646°C, 85.5763°F, 302.9146 K) is used as a temperature reference point. Gallium alloys are used in thermometers as a non-toxic and environmentally friendly alternative to mercury , and can withstand higher temperatures than mercury. A melting point of −19 °C (−2 °F), well below

3420-460: 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

3534-409: Is contained in known reserves of bauxite and zinc ores. Some coal flue dusts contain small quantities of gallium, typically less than 1% by weight. However, these amounts are not extractable without mining of the host materials (see below). Thus, the availability of gallium is fundamentally determined by the rate at which bauxite, zinc ores, and coal are extracted. Gallium is produced exclusively as

Gallium - Misplaced Pages Continue

3648-426: Is further purified with zone melting or single-crystal extraction from a melt ( Czochralski process ). Purities of 99.9999% are routinely achieved and commercially available. Its by-product status means that gallium production is constrained by the amount of bauxite, sulfidic zinc ores (and coal) extracted per year. Therefore, its availability needs to be discussed in terms of supply potential. The supply potential of

3762-482: Is going into (melting) or out of (freezing) the sample when the measurement is made. Only gallium is measured at its melting points; all other metals with defining fixed points on the ITS-90 are measured at their freezing points. A practical effect of the ITS-90 is that the triple points and the freezing/melting points of its thirteen chemical elements are precisely known for all temperature measurements calibrated per

3876-576: Is just above room temperature, and is approximately the same as the average summer daytime temperatures in Earth's mid-latitudes. This melting point (mp) is one of the formal temperature reference points in the International Temperature Scale of 1990 (ITS-90) established by the International Bureau of Weights and Measures (BIPM). The triple point of gallium, 302.9166 K (29.7666 °C, 85.5799 °F),

3990-819: Is not found in nature, but it is easily obtained by smelting . Very pure gallium is a silvery blue metal that fractures conchoidally like glass . Gallium's volume expands by 3.10% when it changes from a liquid to a solid so care must be taken when storing it in containers that may rupture when it changes state. Gallium shares the higher-density liquid state with a short list of other materials that includes water , silicon , germanium , bismuth , and plutonium . Gallium forms alloys with most metals. It readily diffuses into cracks or grain boundaries of some metals such as aluminium, aluminium – zinc alloys and steel , causing extreme loss of strength and ductility called liquid metal embrittlement . The melting point of gallium, at 302.9146 K (29.7646 °C, 85.5763 °F),

4104-436: 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

4218-399: Is one of the four non-radioactive metals (with caesium , rubidium , and mercury ) that are known to be liquid at, or near, normal room temperature. Of the four, gallium is the only one that is neither highly reactive (as are rubidium and caesium) nor highly toxic (as is mercury) and can, therefore, be used in metal-in-glass high-temperature thermometers . It is also notable for having one of

4332-434: Is surrounded by 10 others, rather than 11–12 neighbors typical of most liquid metals. The physical properties of gallium are highly anisotropic , i.e. have different values along the three major crystallographic axes a , b , and c (see table), producing a significant difference between the linear (α) and volume thermal expansion coefficients. The properties of gallium are strongly temperature-dependent, particularly near

4446-542: Is that of a half-sandwich . Less bulky ligands such as mesitylene allow two ligands to be attached to the central gallium atom in a bent sandwich structure. Benzene is even less bulky and allows the formation of dimers: an example is [Ga(η-C 6 H 6 ) 2 ] [GaCl 4 ]·3C 6 H 6 . In 1871, the existence of gallium was first predicted by Russian chemist Dmitri Mendeleev , who named it " eka-aluminium " from its position in his periodic table . He also predicted several properties of eka-aluminium that correspond closely to

4560-426: 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

4674-532: 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

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4788-462: Is unique among the light isotopes in having only electron capture as a decay mode, as its decay energy is not sufficient to allow positron emission. Gallium-67 and gallium-68 (half-life 67.7 min) are both used in nuclear medicine . Gallium is found primarily in the +3 oxidation state . The +1 oxidation state is also found in some compounds, although it is less common than it is for gallium's heavier congeners indium and thallium . For example,

4902-507: Is used by the US National Institute of Standards and Technology (NIST) in preference to the melting point. The melting point of gallium allows it to melt in the human hand, and then solidify if removed. The liquid metal has a strong tendency to supercool below its melting point / freezing point : Ga nanoparticles can be kept in the liquid state below 90 K. Seeding with a crystal helps to initiate freezing. Gallium

5016-417: 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

5130-429: 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

5244-590: 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

5358-450: The Ga(OH) 4 anion. Gallium hydroxide, which is amphoteric , also dissolves in alkali to form gallate salts. Although earlier work suggested Ga(OH) 6 as another possible gallate anion, it was not found in later work. Gallium reacts with the chalcogens only at relatively high temperatures. At room temperature, gallium metal is not reactive with air and water because it forms

5472-489: 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

5586-638: 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

5700-621: The New World . It was used extensively as such by American publications before the international standardization (in 1950). Before chemistry became a science , alchemists designed arcane symbols for both metals and common compounds. These were however used as abbreviations in diagrams or procedures; there was no concept of atoms combining to form molecules . With his advances in the atomic theory of matter, John Dalton devised his own simpler symbols, based on circles, to depict molecules. International Temperature Scale of 1990 In 2019,

5814-423: 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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5928-405: 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

6042-516: The thermodynamic (absolute) temperature scale (referencing absolute zero ) as closely as possible throughout its range. Many different thermometer designs are required to cover the entire range. These include helium vapor pressure thermometers, helium gas thermometers, standard platinum resistance thermometers (known as SPRTs) and monochromatic radiation thermometers . Although the Kelvin and Celsius temperature scales were (until 2019) defined using

6156-401: The triple point of water ( 273.16 K or 0.01 °C ), it is impractical to use this definition at temperatures that are very different from the triple point of water. Accordingly, ITS-90 uses numerous defined points, all of which are based on various thermodynamic equilibrium states of fourteen pure chemical elements and one compound (water). Most of the defined points are based on

6270-638: 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

6384-487: 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

6498-488: The ITS-90 since these thirteen values are fixed by definition. There are often small differences between measurements calibrated per ITS-90 and thermodynamic temperature . For instance, precise measurements show that the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C) when adhering strictly to the two-point definition of thermodynamic temperature. When calibrated to ITS-90, where one must interpolate between

6612-457: The [Ar]3d core. This phenomenon recurs with mercury with its "pseudo-noble-gas" [Xe]4f5d6s electron configuration, which is liquid at room temperature. The 3d electrons do not shield the outer electrons very well from the nucleus and hence the first ionisation energy of gallium is greater than that of aluminium. Ga 2 dimers do not persist in the liquid state and liquid gallium exhibits a complex low-coordinated structure in which each gallium atom

6726-487: 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,

6840-472: The atoms drift over time to measure their temperature. A cesium atom with a velocity of 7 mm/s is equivalent to a temperature of about 700 nK (which was a record cold temperature achieved by the NIST in 1994). Estimates of the differences between thermodynamic temperature and the ITS-90 ( T − T 90 ) were published in 2010. It had become apparent that ITS-90 deviated considerably from PLTS-2000 in

6954-527: The by-product production of gallium will be possible without significant increases in production costs or price. The average price for low-grade gallium was $ 120 per kilogram in 2016 and $ 135–140 per kilogram in 2017. 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

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7068-413: 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

7182-422: The crustal value in zinc ores, and at somewhat higher values (~ 50 ppm) in aluminium ores, from both of which it is extracted as a by-product. This lack of independent deposits is due to gallium's geochemical behaviour, showing no strong enrichment in the processes relevant to the formation of most ore deposits. The United States Geological Survey (USGS) estimates that more than 1 million tons of gallium

7296-408: 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

7410-476: The defining points of gallium and indium, the boiling point of VSMOW water is about 10 mK less, about 99.974 °C. The virtue of ITS-90 is that another lab in another part of the world will measure the very same temperature with ease due to the advantages of a comprehensive international calibration standard featuring many conveniently spaced, reproducible, defining points spanning a wide range of temperatures. Although "International Temperature Scale of 1990" has

7524-579: The density of gallium as 4.7 g/cm, the only property that failed to match Mendeleev's predictions; Mendeleev then wrote to him and suggested that he should remeasure the density, and de Boisbaudran then obtained the correct value of 5.9 g/cm, that Mendeleev had predicted exactly. From its discovery in 1875 until the era of semiconductors, the primary uses of gallium were high-temperature thermometrics and metal alloys with unusual properties of stability or ease of melting (some such being liquid at room temperature). The development of gallium arsenide as

7638-416: 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

7752-533: The element "gallia", from Latin Gallia meaning ' Gaul ', a name for his native land of France. It was later claimed that, in a multilingual pun of a kind favoured by men of science in the 19th century, he had also named gallium after himself: Le coq is French for 'the rooster', and the Latin word for 'rooster' is gallus . In an 1877 article, Lecoq denied this conjecture. Originally, de Boisbaudran determined

7866-406: 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

7980-470: 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

8094-480: 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

8208-413: 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

8322-474: 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

8436-481: The exceptions of quartz, graphite, gallium(III) oxide and PTFE ), making it mechanically more difficult to handle even though it is substantially less toxic and requires far fewer precautions than mercury. Gallium painted onto glass is a brilliant mirror. For this reason as well as the metal contamination and freezing-expansion problems, samples of gallium metal are usually supplied in polyethylene packets within other containers. Gallium does not crystallize in any of

8550-492: 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

8664-630: 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

8778-473: The few high-content minerals, such as gallite (CuGaS 2 ), are too rare to serve as a primary source. The abundance in the Earth's crust is approximately 16.9  ppm . It is the 34th most abundant element in the crust. This is comparable to the crustal abundances of lead , cobalt , and niobium . Yet unlike these elements, gallium does not form its own ore deposits with concentrations of > 0.1 wt.% in ore. Rather it occurs at trace concentrations similar to

8892-529: 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

9006-562: The freezing point of aluminium ( 933.473 K or 660.323 °C ). The defining fixed points of the ITS-90 refer to pure chemical samples with specific isotopic compositions. As a consequence of this, the ITS-90 contains several equations to correct for temperature variations due to impurities and isotopic composition. Thermometers calibrated via the ITS-90 use complex mathematical formulas to interpolate between its defined points. The ITS-90 specifies rigorous control over variables to ensure reproducibility from lab to lab. For instance,

9120-470: The freezing point of water, is claimed for the alloy galinstan (62–⁠95% gallium, 5–⁠22% indium , and 0–⁠16% tin by weight), but that may be the freezing point with the effect of supercooling . Gallium does not occur as a free element in nature, but rather as gallium(III) compounds in trace amounts in zinc ores (such as sphalerite ) and in bauxite . Elemental gallium is a liquid at temperatures greater than 29.76 °C (85.57 °F), and will melt in

9234-431: 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

9348-399: 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

9462-549: 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

9576-415: The hydrated gallium ion, [Ga(H 2 O) 6 ] . Gallium(III) hydroxide , Ga(OH) 3 , may be precipitated from gallium(III) solutions by adding ammonia . Dehydrating Ga(OH) 3 at 100 °C produces gallium oxide hydroxide, GaO(OH). Alkaline hydroxide solutions dissolve gallium, forming gallate salts (not to be confused with identically named gallic acid salts) containing

9690-474: The kelvin was redefined . However, the alteration was very slight compared to the ITS-90 uncertainties, and so the ITS-90 remains the recommended practical temperature scale without any significant changes. It is anticipated that the redefinition, combined with improvements in primary thermometry methods, will phase out reliance on the ITS-90 and the PLTS-2000 in the future. The ITS-90 is designed to represent

9804-402: The largest liquid ranges for a metal, and for having (unlike mercury) a low vapor pressure at high temperatures. Gallium's boiling point, 2676 K, is nearly nine times higher than its melting point on the absolute scale , the greatest ratio between melting point and boiling point of any element. Unlike mercury, liquid gallium metal wets glass and skin, along with most other materials (with

9918-431: The longest-lived (half-life 3.261 days). Isotopes lighter than gallium-69 usually decay through beta plus decay (positron emission) or electron capture to isotopes of zinc , while isotopes heavier than gallium-71 decay through beta minus decay (electron emission), possibly with delayed neutron emission , to isotopes of germanium . Gallium-70 can decay through both beta minus decay and electron capture. Gallium-67

10032-451: The melting point. For example, the coefficient of thermal expansion increases by several hundred percent upon melting. Gallium has 30 known isotopes, ranging in mass number from 60 to 89. Only two isotopes are stable and occur naturally, gallium-69 and gallium-71. Gallium-69 is more abundant: it makes up about 60.1% of natural gallium, while gallium-71 makes up the remaining 39.9%. All the other isotopes are radioactive, with gallium-67 being

10146-506: The order Al > Ga > In and as a result organogallium compounds do not form bridged dimers as organoaluminium compounds do. Organogallium compounds are also less reactive than organoaluminium compounds. They do form stable peroxides. These alkylgalliums are liquids at room temperature, having low melting points, and are quite mobile and flammable. Triphenylgallium is monomeric in solution, but its crystals form chain structures due to weak intermolecluar Ga···C interactions. Gallium trichloride

10260-540: The overlapping range of 0.65 K to 2 K. To address this, a new He vapor pressure scale was adopted, known as PTB-2006 . For higher temperatures, expected values for T − T 90 are below 0.1 mK for temperatures 4.2 K – 8 K, up to 8 mK at temperatures close to 130 K, to 0.1 mK at the triple point of water (273.1600 K), but rising again to 10 mK at temperatures close to 430 K, and reaching 46 mK at temperatures close to 1150 K. The table below lists

10374-418: 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

10488-426: 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,

10602-701: The presence of dimethyl ether as solvent, GaH 3 polymerizes to (GaH 3 ) n . If no solvent is used, the dimer Ga 2 H 6 ( digallane ) is formed as a gas. Its structure is similar to diborane , having two hydrogen atoms bridging the two gallium centers, unlike α- AlH 3 in which aluminium has a coordination number of 6. Gallane is unstable above −10 °C, decomposing to elemental gallium and hydrogen . Organogallium compounds are of similar reactivity to organoindium compounds, less reactive than organoaluminium compounds, but more reactive than organothallium compounds. Alkylgalliums are monomeric. Lewis acidity decreases in

10716-556: The product can be condensed as a red solid. Gallium(I) compounds can be stabilized by forming adducts with Lewis acids. For example: The so-called "gallium(II) halides", GaX 2 , are actually adducts of gallium(I) halides with the respective gallium(III) halides, having the structure Ga [GaX 4 ] . For example: Like aluminium , gallium also forms a hydride , GaH 3 , known as gallane , which may be produced by reacting lithium gallanate ( LiGaH 4 ) with gallium(III) chloride at −30 °C: In

10830-412: 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

10944-491: The reaction of gallium metal with chlorine gas. Unlike the trifluoride, gallium(III) chloride exists as dimeric molecules, Ga 2 Cl 6 , with a melting point of 78 °C. Equivalent compounds are formed with bromine and iodine, Ga 2 Br 6 and Ga 2 I 6 . Like the other group 13 trihalides, gallium(III) halides are Lewis acids , reacting as halide acceptors with alkali metal halides to form salts containing GaX 4 anions, where X

11058-468: The reaction of gallium with hydrogen sulfide ( H 2 S ) at 950 °C. Alternatively, Ga(OH) 3 can be used at 747 °C: Reacting a mixture of alkali metal carbonates and Ga 2 O 3 with H 2 S leads to the formation of thiogallates containing the [Ga 2 S 4 ] anion. Strong acids decompose these salts, releasing H 2 S in the process. The mercury salt, HgGa 2 S 4 , can be used as

11172-772: 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

11286-546: The real properties of gallium, such as its density , melting point , oxide character, and bonding in chloride. Mendeleev further predicted that eka-aluminium would be discovered by means of the spectroscope , and that metallic eka-aluminium would dissolve slowly in both acids and alkalis and would not react with air. He also predicted that M 2 O 3 would dissolve in acids to give MX 3 salts, that eka- aluminium salts would form basic salts, that eka-aluminium sulfate should form alums , and that anhydrous MCl 3 should have

11400-919: 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,

11514-624: 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

11628-495: 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

11742-404: 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

11856-718: The same structure as ZnS , and have important semiconducting properties. GaP, GaAs, and GaSb can be synthesized by the direct reaction of gallium with elemental phosphorus, arsenic, or antimony. They exhibit higher electrical conductivity than GaN. GaP can also be synthesized by reacting Ga 2 O with phosphorus at low temperatures. Gallium forms ternary nitrides ; for example: Similar compounds with phosphorus and arsenic are possible: Li 3 GaP 2 and Li 3 GaAs 2 . These compounds are easily hydrolyzed by dilute acids and water. Gallium(III) oxide reacts with fluorinating agents such as HF or F 2 to form gallium(III) fluoride , GaF 3 . It

11970-457: 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

12084-479: The simple crystal structures . The stable phase under normal conditions is orthorhombic with 8 atoms in the conventional unit cell . Within a unit cell, each atom has only one nearest neighbor (at a distance of 244  pm ). The remaining six unit cell neighbors are spaced 27, 30 and 39 pm farther away, and they are grouped in pairs with the same distance. Many stable and metastable phases are found as function of temperature and pressure. The bonding between

12198-491: The small effect that atmospheric pressure has upon the various melting points is compensated for (an effect that typically amounts to no more than half a millikelvin across the different altitudes and barometric pressures likely to be encountered). The standard also compensates for the pressure effect due to how deeply the temperature probe is immersed into the sample. The ITS-90 also draws a distinction between "freezing" and "melting" points. The distinction depends on whether heat

12312-496: 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

12426-955: 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

12540-416: The two nearest neighbors is covalent ; hence Ga 2 dimers are seen as the fundamental building blocks of the crystal. This explains the low melting point relative to the neighbor elements, aluminium and indium. This structure is strikingly similar to that of iodine and may form because of interactions between the single 4p electrons of gallium atoms, further away from the nucleus than the 4s electrons and

12654-621: 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

12768-591: The very stable GaCl 2 contains both gallium(I) and gallium(III) and can be formulated as GaGaCl 4 ; in contrast, the monochloride is unstable above 0 °C, disproportionating into elemental gallium and gallium(III) chloride. Compounds containing Ga–Ga bonds are true gallium(II) compounds, such as GaS (which can be formulated as Ga 2 (S) 2 ) and the dioxan complex Ga 2 Cl 4 (C 4 H 8 O 2 ) 2 . Strong acids dissolve gallium, forming gallium(III) salts such as Ga(NO 3 ) 3 (gallium nitrate). Aqueous solutions of gallium(III) salts contain

12882-463: The word "scale" in its title, this is a misnomer that can be misleading. The ITS-90 is not a scale; it is an equipment calibration standard . Temperatures measured with equipment calibrated per ITS-90 may be expressed using any temperature scale such as Celsius, Kelvin, Fahrenheit, or Rankine. For example, a temperature can be measured using equipment calibrated to the kelvin-based ITS-90 standard, and that value may then be converted to, and expressed as,

12996-528: 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,

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