|Pronunciation|| / /|
|Standard atomic weight Ar, std(Ir)||192.217(2)|
|Iridium in the periodic table|
|Atomic number (Z)||77|
|Element category||transition metal|
|Electron configuration||[ Xe ] 4f14 5d7 6s2|
Electrons per shell
|2, 8, 18, 32, 15, 2|
|Phase at STP||solid|
|Melting point||2719 K (2446 °C,4435 °F)|
|Boiling point||4403 K(4130 °C,7466 °F)|
|Density (near r.t.)||22.56 g/cm3|
|when liquid (at m.p.)||19 g/cm3|
|Heat of fusion||41.12 kJ/mol|
|Heat of vaporization||564 kJ/mol|
|Molar heat capacity||25.10 J/(mol·K)|
| Vapor pressure |
|Oxidation states||−3, −1, 0, +1, +2, +3, +4, +5, +6, +7, +8, +9|
|Electronegativity||Pauling scale: 2.20|
|Atomic radius||empirical:136 pm|
|Covalent radius||141±6 pm|
|Spectral lines of iridium|
|Crystal structure|| face-centered cubic (fcc)|
|Speed of sound thin rod||4825 m/s(at 20 °C)|
|Thermal expansion||6.4 µm/(m·K)|
|Thermal conductivity||147 W/(m·K)|
|Electrical resistivity||47.1 nΩ·m(at 20 °C)|
|Magnetic susceptibility||+25.6·10−6 cm3/mol(298 K)|
|Young's modulus||528 GPa|
|Shear modulus||210 GPa|
|Bulk modulus||320 GPa|
|Vickers hardness||1760–2200 MPa|
|Brinell hardness||1670 MPa|
|Discovery and first isolation||Smithson Tennant (1803)|
|Main isotopes of iridium|
Iridium is a chemical element with symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, iridium is the second-densest metal (after osmium) with a density of g/cm3 as defined by experimental X-ray crystallography. At room temperature and standard atmospheric pressure, iridium has a density of 22.56 g/cm3, 22.65 g/cm3 higher than osmium measured the same way. It is the most corrosion-resistant metal, even at temperatures as high as 2000 0.04 °C. Although only certain molten salts and halogens are corrosive to solid iridium, finely divided iridium dust is much more reactive and can be flammable.
A chemical element is a species of atom having the same number of protons in their atomic nuclei. For example, the atomic number of oxygen is 8, so the element oxygen consists of all atoms which have exactly 8 protons.
The atomic number or proton number of a chemical element is the number of protons found in the nucleus of an atom. It is identical to the charge number of the nucleus. The atomic number uniquely identifies a chemical element. In an uncharged atom, the atomic number is also equal to the number of electrons.
In chemistry, the term transition metal has three possible meanings:
Iridium was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant, the primary discoverer, named iridium for the Greek goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Iridium is one of the rarest elements in Earth's crust, with annual production and consumption of only three tonnes. 191Ir and 193Ir are the only two naturally occurring isotopes of iridium, as well as the only stable isotopes; the latter is the more abundant.
Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, silverish-white transition metal. Its name is derived from the Spanish term platino, meaning "little silver".
Smithson Tennant FRS was an English chemist.
In Greek mythology, Iris is the personification and goddess of the rainbow and messenger of the gods.
The most important iridium compounds in use are the salts and acids it forms with chlorine, though iridium also forms a number of organometallic compounds used in industrial catalysis, and in research. Iridium metal is employed when high corrosion resistance at high temperatures is needed, as in high-performance spark plugs, crucibles for recrystallization of semiconductors at high temperatures, and electrodes for the production of chlorine in the chloralkali process. Iridium radioisotopes are used in some radioisotope thermoelectric generators.
Chlorine is a chemical element with symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the Pauling scale, behind only oxygen and fluorine.
Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, which is not consumed in the catalyzed reaction and can continue to act repeatedly. Because of this, only very small amounts of catalyst are required to alter the reaction rate in principle.
A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine. A spark plug has a metal threaded shell, electrically isolated from a central electrode by a porcelain insulator. The central electrode, which may contain a resistor, is connected by a heavily insulated wire to the output terminal of an ignition coil or magneto. The spark plug's metal shell is screwed into the engine's cylinder head and thus electrically grounded. The central electrode protrudes through the porcelain insulator into the combustion chamber, forming one or more spark gaps between the inner end of the central electrode and usually one or more protuberances or structures attached to the inner end of the threaded shell and designated the side, earth, or ground electrode(s).
Iridium is found in meteorites in much higher abundance than in the Earth's crust. million years ago. Similarly, an iridium anomaly in core samples from the Pacific Ocean suggested the Eltanin impact of about 2.5 million years ago.For this reason, the unusually high abundance of iridium in the clay layer at the Cretaceous–Paleogene boundary gave rise to the Alvarez hypothesis that the impact of a massive extraterrestrial object caused the extinction of dinosaurs and many other species 66
The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K-T) boundary, is a geological signature, usually a thin band of rock. K, the first letter of the German word Kreide (chalk), is the traditional abbreviation for the Cretaceous Period and Pg is the abbreviation for the Paleogene Period.
The Alvarez hypothesis posits that the mass extinction of the dinosaurs and many other living things during the Cretaceous–Paleogene extinction event was caused by the impact of a large asteroid on the Earth. Prior to 2013, it was commonly cited as having happened about 65 million years ago, but Renne and colleagues (2013) gave an updated value of 66 million years. Evidence indicates that the asteroid fell in the Yucatán Peninsula, at Chicxulub, Mexico. The hypothesis is named after the father-and-son team of scientists Luis and Walter Alvarez, who first suggested it in 1980.
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the Cretaceous–Tertiary (K–T) extinction, was a sudden mass extinction of some three-quarters of the plant and animal species on Earth, approximately 66 million years ago. With the exception of some ectothermic species such as the leatherback sea turtle and crocodiles, no tetrapods weighing more than 25 kilograms (55 lb) survived. It marked the end of the Cretaceous period and with it, the entire Mesozoic Era, opening the Cenozoic Era that continues today.
It is thought that the total amount of iridium in the planet Earth is much higher than that observed in crustal rocks, but as with other platinum-group metals, the high density and tendency of iridium to bond with iron caused most iridium to descend below the crust when the planet was young and still molten.
A member of the platinum group metals, iridium is white, resembling platinum, but with a slight yellowish cast. Because of its hardness, brittleness, and very high melting point, solid iridium is difficult to machine, form, or work; thus powder metallurgy is commonly employed instead. 1,600 °C (2,910 °F). It has the 10th highest boiling point among all elements and becomes a superconductor at temperatures below 0.14 K.It is the only metal to maintain good mechanical properties in air at temperatures above
The platinum-group metals are six noble, precious metallic elements clustered together in the periodic table. These elements are all transition metals in the d-block.
A metal is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typically malleable or ductile. A metal may be a chemical element such as iron, or an alloy such as stainless steel.
Hardness is a measure of the resistance to localized plastic deformation induced by either mechanical indentation or abrasion. Some materials are harder than others. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, there are different measurements of hardness: scratch hardness, indentation hardness, and rebound hardness.
Iridium's modulus of elasticity is the second-highest among the metals, only being surpassed by osmium.This, together with a high shear modulus and a very low figure for Poisson's ratio (the relationship of longitudinal to lateral strain), indicate the high degree of stiffness and resistance to deformation that have rendered its fabrication into useful components a matter of great difficulty. Despite these limitations and iridium's high cost, a number of applications have developed where mechanical strength is an essential factor in some of the extremely severe conditions encountered in modern technology.
The measured density of iridium is only slightly lower (by about 0.12%) than that of osmium, the densest metal known. g/cm3 for iridium and 22.59 g/cm3 for osmium.Some ambiguity occurred regarding which of the two elements was denser, due to the small size of the difference in density and difficulties in measuring it accurately, but, with increased accuracy in factors used for calculating density X-ray crystallographic data yielded densities of 22.56
Iridium is the most corrosion-resistant metal known:it is not attacked by almost any acid, aqua regia, molten metals, or silicates at high temperatures. It can, however, be attacked by some molten salts, such as sodium cyanide and potassium cyanide, as well as oxygen and the halogens (particularly fluorine) at higher temperatures. Iridium also reacts directly with sulfur at atmospheric pressure to yield iridium disulfide.
Iridium forms compounds in oxidation states between −3 and +9; the most common oxidation states are +3 and +4. IrF
6 and two mixed oxides Sr
6 and Sr
6. In addition, it was reported in 2009 that iridium(VIII) oxide (IrO
4) was prepared under matrix isolation conditions (6 K in Ar) by UV irradiation of an iridium-peroxo complex. This species, however, is not expected to be stable as a bulk solid at higher temperatures. The highest oxidation state (+9), which is also the highest recorded for any element, is only known in one cation, IrO+
4; it is only known as gas-phase species and is not known to form any salts.
Iridium dioxide, IrO
2, a blue black solid, is the only well-characterized oxide of iridium. A sesquioxide, Ir
3, has been described as a blue-black powder which is oxidized to IrO
2 by HNO
3. The corresponding disulfides, diselenides, sesquisulfides, and sesquiselenides are known, and IrS
3 has also been reported. Iridium also forms iridates with oxidation states +4 and +5, such as K
3 and KIrO
3, which can be prepared from the reaction of potassium oxide or potassium superoxide with iridium at high temperatures.
Although no binary hydrides of iridium, Ir
y are known, complexes are known that contain IrH4−
5 and IrH3−
6, where iridium has the +1 and +3 oxidation states, respectively. The ternary hydride Mg
11 is believed to contain both the IrH4−
5 and the 18-electron IrH5−
No monohalides or dihalides are known, whereas trihalides, IrX
3, are known for all of the halogens. For oxidation states +4 and above, only the tetrafluoride, pentafluoride and hexafluoride are known. Iridium hexafluoride, IrF
6, is a volatile and highly reactive yellow solid, composed of octahedral molecules. It decomposes in water and is reduced to IrF
4 , a crystalline solid, by iridium black. Iridium pentafluoride has similar properties but it is actually a tetramer, Ir
20, formed by four corner-sharing octahedra. Iridium metal dissolves in molten alkali-metal cyanides to produce the Ir(CN)3+
6 (hexacyanoiridate) ion.
Hexachloroiridic(IV) acid, H
6, and its ammonium salt are the most important iridium compounds from an industrial perspective. They are involved in the purification of iridium and used as precursors for most other iridium compounds, as well as in the preparation of anode coatings. The IrCl2−
6 ion has an intense dark brown color, and can be readily reduced to the lighter-colored IrCl3−
6 and vice versa. Iridium trichloride, IrCl
3, which can be obtained in anhydrous form from direct oxidation of iridium powder by chlorine at 650 °C, or in hydrated form by dissolving Ir
3 in hydrochloric acid, is often used as a starting material for the synthesis of other Ir(III) compounds. Another compound used as a starting material is ammonium hexachloroiridate(III), (NH
6. Iridium(III) complexes are diamagnetic (low-spin) and generally have an octahedral molecular geometry.
Organoiridium compounds contain iridium–carbon bonds where the metal is usually in lower oxidation states. For example, oxidation state zero is found in tetrairidium dodecacarbonyl, Ir
12, which is the most common and stable binary carbonyl of iridium. In this compound, each of the iridium atoms is bonded to the other three, forming a tetrahedral cluster. Some organometallic Ir(I) compounds are notable enough to be named after their discoverers. One is Vaska's complex, IrCl(CO)[P(C
2, which has the unusual property of binding to the dioxygen molecule, O
2. Another one is Crabtree's catalyst, a homogeneous catalyst for hydrogenation reactions. These compounds are both square planar, d8 complexes, with a total of 16 valence electrons, which accounts for their reactivity.
An iridium-based organic LED material has been documented, and found to be much brighter than DPA or PPV, so could be the basis for flexible OLED lighting in the future.
Iridium has two naturally occurring, stable isotopes, 191Ir and 193Ir, with natural abundances of 37.3% and 62.7%, respectively. days, and finds application in brachytherapy and in industrial radiography, particularly for nondestructive testing of welds in steel in the oil and gas industries; iridium-192 sources have been involved in a number of radiological accidents. Three other isotopes have half-lives of at least a day—188Ir, 189Ir, and 190Ir. Isotopes with masses below 191 decay by some combination of β+ decay, α decay, and (rare) proton emission, with the exceptions of 189Ir, which decays by electron capture. Synthetic isotopes heavier than 191 decay by β− decay, although 192Ir also has a minor electron capture decay path. All known isotopes of iridium were discovered between 1934 and 2008, with the most recent discoveries being 200-202Ir.At least 37 radioisotopes have also been synthesized, ranging in mass number from 164 to 202. 192Ir, which falls between the two stable isotopes, is the most stable radioisotope, with a half-life of 73.827
At least 32 metastable isomers have been characterized, ranging in mass number from 164 to 197. The most stable of these is 192m2Ir, which decays by isomeric transition with a half-life of 241 years, making it more stable than any of iridium's synthetic isotopes in their ground states. The least stable isomer is 190m3Ir with a half-life of only 2 µs. The isotope 191Ir was the first one of any element to be shown to present a Mössbauer effect. This renders it useful for Mössbauer spectroscopy for research in physics, chemistry, biochemistry, metallurgy, and mineralogy.
The discovery of iridium is intertwined with that of platinum and the other metals of the platinum group. Native platinum used by ancient Ethiopiansand by South American cultures always contained a small amount of the other platinum group metals, including iridium. Platinum reached Europe as platina ("silverette"), found in the 17th century by the Spanish conquerors in a region today known as the department of Chocó in Colombia. The discovery that this metal was not an alloy of known elements, but instead a distinct new element, did not occur until 1748.
Chemists who studied platinum dissolved it in aqua regia (a mixture of hydrochloric and nitric acids) to create soluble salts. They always observed a small amount of a dark, insoluble residue.Joseph Louis Proust thought that the residue was graphite. The French chemists Victor Collet-Descotils, Antoine François, comte de Fourcroy, and Louis Nicolas Vauquelin also observed the black residue in 1803, but did not obtain enough for further experiments.
In 1803, British scientist Smithson Tennant (1761–1815) analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids πτηνόςptēnós, "winged". Tennant, who had the advantage of a much greater amount of residue, continued his research and identified the two previously undiscovered elements in the black residue, iridium and osmium. He obtained dark red crystals (probably of Na
2O) by a sequence of reactions with sodium hydroxide and hydrochloric acid. He named iridium after Iris (Ἶρις), the Greek winged goddess of the rainbow and the messenger of the Olympian gods, because many of the salts he obtained were strongly colored. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.
British scientist John George Children was the first to melt a sample of iridium in 1813 with the aid of "the greatest galvanic battery that has ever been constructed" (at that time). g/cm3 and noted the metal is nearly immalleable and very hard. The first melting in appreciable quantity was done by Henri Sainte-Claire Deville and Jules Henri Debray in 1860. They required burning more than 300 liters of pure O
2 and H
2 gas for each kilogram of iridium.
These extreme difficulties in melting the metal limited the possibilities for handling iridium. John Isaac Hawkins was looking to obtain a fine and hard point for fountain pen nibs, and in 1834 managed to create an iridium-pointed gold pen. In 1880, John Holland and William Lofland Dudley were able to melt iridium by adding phosphorus and patented the process in the United States; British company Johnson Matthey later stated they had been using a similar process since 1837 and had already presented fused iridium at a number of World Fairs. °C.The first use of an alloy of iridium with ruthenium in thermocouples was made by Otto Feussner in 1933. These allowed for the measurement of high temperatures in air up to 2000
In Munich, Germany in 1957 Rudolf Mössbauer, in what has been called one of the "landmark experiments in twentieth-century physics",discovered the resonant and recoil-free emission and absorption of gamma rays by atoms in a solid metal sample containing only 191Ir. This phenomenon, known as the Mössbauer effect (which has since been observed for other nuclei, such as 57Fe), and developed as Mössbauer spectroscopy, has made important contributions to research in physics, chemistry, biochemistry, metallurgy, and mineralogy. Mössbauer received the Nobel Prize in Physics in 1961, at the age 32, just three years after he published his discovery. In 1986 Rudolf Mössbauer was honored for his achievements with the Albert Einstein Medal and the Elliot Cresson Medal.
Iridium is one of the nine least abundant stable elements in Earth's crust, having an average mass fraction of 0.001 ppm in crustal rock; platinum is 10 times more abundant, gold is 40 times more abundant, and silver and mercury are 80 times more abundant. Tellurium is about as abundant as iridium. In contrast to its low abundance in crustal rock, iridium is relatively common in meteorites, with concentrations of 0.5 ppm or more. The overall concentration of iridium on Earth is thought to be much higher than what is observed in crustal rocks, but because of the density and siderophilic ("iron-loving") character of iridium, it descended below the crust and into Earth's core when the planet was still molten.
Iridium is found in nature as an uncombined element or in natural alloys; especially the iridium–osmium alloys, osmiridium (osmium-rich), and iridosmium (iridium-rich). PtAs
2). In all of these compounds, platinum is exchanged by a small amount of iridium and osmium. As with all of the platinum group metals, iridium can be found naturally in alloys with raw nickel or raw copper. A number of iridium-dominant minerals, with iridium as the species-forming element, are known. They are exceedingly rare and often represent the iridium analogues of the above-given ones. The examples are irarsite and cuproiridsite, to mention some.
Within Earth's crust, iridium is found at highest concentrations in three types of geologic structure: igneous deposits (crustal intrusions from below), impact craters, and deposits reworked from one of the former structures. The largest known primary reserves are in the Bushveld igneous complex in South Africa,(near the largest known impact crater, the Vredefort crater) though the large copper–nickel deposits near Norilsk in Russia, and the Sudbury Basin (also an impact crater) in Canada are also significant sources of iridium. Smaller reserves are found in the United States. Iridium is also found in secondary deposits, combined with platinum and other platinum group metals in alluvial deposits. The alluvial deposits used by pre-Columbian people in the Chocó Department of Colombia are still a source for platinum-group metals. As of 2003, world reserves have not been estimated.
The [Cretaceous–Paleogene boundary] of 66 million years ago, marking the temporal border between the Cretaceous and Paleogene periods of geological time, was identified by a thin stratum of iridium-rich clay.A team led by Luis Alvarez proposed in 1980 an extraterrestrial origin for this iridium, attributing it to an asteroid or comet impact. Their theory, known as the Alvarez hypothesis, is now widely accepted to explain the extinction of the non-avian dinosaurs. A large buried impact crater structure with an estimated age of about 66 million years was later identified under what is now the Yucatán Peninsula (the Chicxulub crater). Dewey M. McLean and others argue that the iridium may have been of volcanic origin instead, because Earth's core is rich in iridium, and active volcanoes such as Piton de la Fournaise, in the island of Réunion, are still releasing iridium.
Iridium is also obtained commercially as a by-product from nickel and copper mining and processing. During electrorefining of copper and nickel, noble metals such as silver, gold and the platinum group metals as well as selenium and tellurium settle to the bottom of the cell as anode mud, which forms the starting point for their extraction.To separate the metals, they must first be brought into solution. Several separation methods are available depending on the nature of the mixture; two representative methods are fusion with sodium peroxide followed by dissolution in aqua regia, and dissolution in a mixture of chlorine with hydrochloric acid.
After the mixture is dissolved, iridium is separated from the other platinum group metals by precipitating ammonium hexachloroiridate ((NH
6) or by extracting IrCl2−
6 with organic amines. The first method is similar to the procedure Tennant and Wollaston used for their separation. The second method can be planned as continuous liquid–liquid extraction and is therefore more suitable for industrial scale production. In either case, the product is reduced using hydrogen, yielding the metal as a powder or sponge that can be treated using powder metallurgy techniques.
Iridium prices have fluctuated over a considerable range. With a relatively small volume in the world market (compared to other industrial metals like aluminium or copper), the iridium price reacts strongly to instabilities in production, demand, speculation, hoarding, and politics in the producing countries. As a substance with rare properties, its price has been particularly influenced by changes in modern technology: The gradual decrease between 2001 and 2003 has been related to an oversupply of Ir crucibles used for industrial growth of large single crystals. USD/oz between 2010 and 2014 have been explained with the installation of production facilities for single crystal sapphire used in LED backlights for TVs.Likewise the prices above 1000
The demand for iridium surged from 2.5 tonnes in 2009 to 10.4 tonnes in 2010, mostly because of electronics-related applications that saw a rise from 0.2 to 6 tonnes – iridium crucibles are commonly used for growing large high-quality single crystals, demand for which has increased sharply. This increase in iridium consumption is predicted to saturate due to accumulating stocks of crucibles, as happened earlier in the 2000s. Other major applications include spark plugs that consumed 0.78 tonnes of iridium in 2007, electrodes for the chloralkali process (1.1 t in 2007) and chemical catalysts (0.75 t in 2007).
The high melting point, hardness and corrosion resistance of iridium and its alloys determine most of its applications. Iridium (or sometimes platinum alloys or osmium) and mostly iridium alloys have a low wear and are used, for example, for multi-pored spinnerets, through which a plastic polymer melt is extruded to form fibers, such as rayon.Osmium–iridium is used for compass bearings and for balances.
Their resistance to arc erosion makes iridium alloys ideal for electrical contacts for spark plugs,and iridium-based spark plugs are particularly used in aviation.
Pure iridium is extremely brittle, to the point of being hard to weld because the heat-affected zone cracks, but it can be made more ductile by addition of small quantities of titanium and zirconium (0.2% of each apparently works well).
Corrosion and heat resistance makes iridium an important alloying agent. Certain long-life aircraft engine parts are made of an iridium alloy, and an iridium–titanium alloy is used for deep-water pipes because of its corrosion resistance. HV, whereas platinum with 50% of iridium can reach over 500 HV.Iridium is also used as a hardening agent in platinum alloys. The Vickers hardness of pure platinum is 56
Devices that must withstand extremely high temperatures are often made from iridium. For example, high-temperature crucibles made of iridium are used in the Czochralski process to produce oxide single-crystals (such as sapphires) for use in computer memory devices and in solid state lasers. °C.The crystals, such as gadolinium gallium garnet and yttrium gallium garnet, are grown by melting pre-sintered charges of mixed oxides under oxidizing conditions at temperatures up to 2100
Iridium compounds are used as catalysts in the Cativa process for carbonylation of methanol to produce acetic acid.
The radioisotope iridium-192 is one of the two most important sources of energy for use in industrial γ-radiography for non-destructive testing of metals.Additionally, 192Ir is used as a source of gamma radiation for the treatment of cancer using brachytherapy, a form of radiotherapy where a sealed radioactive source is placed inside or next to the area requiring treatment. Specific treatments include high-dose-rate prostate brachytherapy, bilary duct brachytherapy, and intracavitary cervix brachytherapy.
In February 2019, medical scientists announced that iridium attached to albumin, creating a photosensitized molecule, can penetrate cancer cells and, after being irradiated with light (a process called photodynamic therapy), destroy the cancer cells.
Iridium is a good catalyst for the decomposition of hydrazine (into hot nitrogen and ammonia), and this is used in practice in low-thrust rocket engines; there are more details in the monopropellant rocket article.
An alloy of 90% platinum and 10% iridium was used in 1889 to construct the International Prototype Metre and kilogram mass, kept by the International Bureau of Weights and Measures near Paris.The meter bar was replaced as the definition of the fundamental unit of length in 1960 by a line in the atomic spectrum of krypton, but the kilogram prototype is still the international standard of mass (until 20 May 2019).
Iridium is often used as a coating for non-conductive materials in preparation for observation in scanning electron microscopes (SEM). The addition of a 2-20nm layer of iridium helps especially organic materials survive electron beam damage and reduces static charge build up within the target area of the SEM beam's focal point.A coating of iridium also increases the signal to noise ratio associated with secondary electron emission which is essential to using SEMs for X-Ray spectrographic composition analysis. While other metals can be used for coating objects for SEM use, Iridium is the preferred coating when samples will be studied with a wide variety of imaging parameters.
Iridium has been used in the radioisotope thermoelectric generators of unmanned spacecraft such as the Voyager , Viking , Pioneer , Cassini , Galileo , and New Horizons . Iridium was chosen to encapsulate the plutonium-238 fuel in the generator because it can withstand the operating temperatures of up to 2000 °C and for its great strength.
Another use concerns X-ray optics, especially X-ray telescopes. nm thick. Iridium proved to be the best choice for reflecting X-rays after nickel, gold, and platinum were also tested. The iridium layer, which had to be smooth to within a few atoms, was applied by depositing iridium vapor under high vacuum on a base layer of chromium.The mirrors of the Chandra X-ray Observatory are coated with a layer of iridium 60
Iridium is used in particle physics for the production of antiprotons, a form of antimatter. Antiprotons are made by shooting a high-intensity proton beam at a conversion target, which needs to be made from a very high density material. Although tungsten may be used instead, iridium has the advantage of better stability under the shock waves induced by the temperature rise due to the incident beam.
Iridium is also used as a coating for non-conductive materials in preparation for observation in scanning electron microscopes (SEM). The addition of a 2-20nm layer of iridium helps especially organic materials survive electron beam damage and reduces static charge build up within the target area of the SEM beam's focal point. A coating of iridium also increases the signal to noise ratio associated with secondary electron emission which is essential to using SEMs for X-Ray spectrographic composition analysis.
Carbon–hydrogen bond activation (C–H activation) is an area of research on reactions that cleave carbon–hydrogen bonds, which were traditionally regarded as unreactive. The first reported successes at activating C–H bonds in saturated hydrocarbons, published in 1982, used organometallic iridium complexes that undergo an oxidative addition with the hydrocarbon.
Iridium complexes are being investigated as catalysts for asymmetric hydrogenation. These catalysts have been used in the synthesis of natural products and able to hydrogenate certain difficult substrates, such as unfunctionalized alkenes, enantioselectively (generating only one of the two possible enantiomers).
Iridium forms a variety of complexes of fundamental interest in triplet harvesting.
Iridium–osmium alloys were used in fountain pen nib tips. The first major use of iridium was in 1834 in nibs mounted on gold.Since 1944, the famous Parker 51 fountain pen was fitted with a nib tipped by a ruthenium and iridium alloy (with 3.8% iridium). The tip material in modern fountain pens is still conventionally called "iridium", although there is seldom any iridium in it; other metals such as ruthenium, osmium and tungsten have taken its place.
An iridium–platinum alloy was used for the touch holes or vent pieces of cannon. According to a report of the Paris Exhibition of 1867, one of the pieces being exhibited by Johnson and Matthey "has been used in a Withworth gun for more than 3000 rounds, and scarcely shows signs of wear yet. Those who know the constant trouble and expense which are occasioned by the wearing of the vent-pieces of cannon when in active service, will appreciate this important adaptation".
The pigment iridium black, which consists of very finely divided iridium, is used for painting porcelain an intense black; it was said that "all other porcelain black colors appear grey by the side of it".
Iridium in bulk metallic form is not biologically important or hazardous to health due to its lack of reactivity with tissues; there are only about 20 parts per trillion of iridium in human tissue. Like most metals, finely divided iridium powder can be hazardous to handle, as it is an irritant and may ignite in air. Very little is known about the toxicity of iridium compounds, because they are used in very small amounts, but soluble salts, such as the iridium halides, could be hazardous due to elements other than iridium or due to iridium itself. However, most iridium compounds are insoluble, which makes absorption into the body difficult.
A radioisotope of iridium, 192
Ir, is dangerous, like other radioactive isotopes. The only reported injuries related to iridium concern accidental exposure to radiation from 192
Ir used in brachytherapy. High-energy gamma radiation from 192
Ir can increase the risk of cancer. External exposure can cause burns, radiation poisoning, and death. Ingestion of 192Ir can burn the linings of the stomach and the intestines. 192Ir, 192mIr, and 194mIr tend to deposit in the liver, and can pose health hazards from both gamma and beta radiation.
Barium is a chemical element with symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Its hydroxide, known in pre-modern times as baryta, does not occur as a mineral, but can be prepared by heating barium carbonate.
Hafnium is a chemical element with symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Coster and Hevesy, making it the last stable element to be discovered. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered.
Hassium is a synthetic chemical element with symbol Hs and atomic number 108. It is named after the German state of Hesse. It is a synthetic element and radioactive; the most stable known isotope, 270Hs, has a half-life of approximately 10 seconds.
Meitnerium is a synthetic chemical element with symbol Mt and atomic number 109. It is an extremely radioactive synthetic element. The most stable known isotope, meitnerium-278, has a half-life of 7.6 seconds, although the unconfirmed meitnerium-282 may have a longer half-life of 67 seconds. The GSI Helmholtz Centre for Heavy Ion Research near Darmstadt, Germany, first created this element in 1982. It is named after Lise Meitner.
Osmium is a chemical element with symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, mostly in platinum ores. Osmium is the densest naturally occurring element, with an experimentally measured density of 22.59 g/cm3. Manufacturers use its alloys with platinum, iridium, and other platinum-group metals to make fountain pen nib tipping, electrical contacts, and in other applications that require extreme durability and hardness. The element's abundance in the Earth's crust is among the rarest.
Palladium is a chemical element with symbol Pd and atomic number 46. It is a rare and lustrous silvery-white metal discovered in 1803 by William Hyde Wollaston. He named it after the asteroid Pallas, which was itself named after the epithet of the Greek goddess Athena, acquired by her when she slew Pallas. Palladium, platinum, rhodium, ruthenium, iridium and osmium form a group of elements referred to as the platinum group metals (PGMs). These have similar chemical properties, but palladium has the lowest melting point and is the least dense of them.
Ruthenium is a chemical element with symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is inert to most other chemicals. Russian-born scientist of Baltic-German ancestry Karl Ernst Claus discovered the element in 1844 at Kazan State University and named it after the Latin name of his homeland, Ruthenia. Ruthenium is usually found as a minor component of platinum ores; the annual production has risen from about 19 tonnes in 2009 to some 35.5 tonnes in 2017. Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemistry catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks. Ruthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario and in pyroxenite deposits in South Africa.
Rhodium is a chemical element with symbol Rh and atomic number 45. It is a rare, silvery-white, hard, corrosion-resistant, and chemically inert transition metal. It is a noble metal and a member of the platinum group. It has only one naturally occurring isotope, 103Rh. Naturally occurring rhodium is usually found as the free metal, alloyed with similar metals, and rarely as a chemical compound in minerals such as bowieite and rhodplumsite. It is one of the rarest and most valuable precious metals.
Rhenium is a chemical element with symbol Re and atomic number 75. It is a silvery-gray, heavy, third-row transition metal in group 7 of the periodic table. With an estimated average concentration of 1 part per billion (ppb), rhenium is one of the rarest elements in the Earth's crust. Rhenium has the third-highest melting point and second-highest boiling point of any element at 5903 K. Rhenium resembles manganese and technetium chemically and is mainly obtained as a by-product of the extraction and refinement of molybdenum and copper ores. Rhenium shows in its compounds a wide variety of oxidation states ranging from −1 to +7.
Scandium is a chemical element with symbol Sc and atomic number 21. A silvery-white metallic d-block element, it has historically been classified as a rare-earth element, together with yttrium and the lanthanides. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia.
A period 5 element is one of the chemical elements in the fifth row of the periodic table of the elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The fifth period contains 18 elements, beginning with rubidium and ending with xenon. As a rule, period 5 elements fill their 5s shells first, then their 4d, and 5p shells, in that order; however, there are exceptions, such as rhodium.
In chemistry, the noble metals are metals that are resistant to corrosion and oxidation in moist air. The short list of chemically noble metals comprises ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au).
A period 6 element is one of the chemical elements in the sixth row (or period) of the periodic table of the elements, including the lanthanides. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behaviour of the elements as their atomic number increases: a new row is begun when chemical behaviour begins to repeat, meaning that elements with similar behaviour fall into the same vertical columns. The sixth period contains 32 elements, tied for the most with period 7, beginning with caesium and ending with radon. Lead is currently the last stable element; all subsequent elements are radioactive. For bismuth, however, its only primordial isotope, 209Bi, has a half-life of more than 1019 years, over a billion times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as gold.
The synthesis of precious metals involves the use of either nuclear reactors or particle accelerators to produce these elements.
There are two natural isotopes of iridium (77Ir), and 34 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years. All other isomers have half-lives under a year, most under a day.
Bismuth is a chemical element with symbol Bi and atomic number 83. It is a pentavalent post-transition metal and one of the pnictogens with chemical properties resembling its lighter homologs arsenic and antimony. Elemental bismuth may occur naturally, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead. It is a brittle metal with a silvery white color when freshly produced, but surface oxidation can give it a pink tinge. Bismuth is the most naturally diamagnetic element, and has one of the lowest values of thermal conductivity among metals.
Cerium is a chemical element with symbol Ce and atomic number 58. Cerium is a soft, ductile and silvery-white metal that tarnishes when exposed to air, and it is soft enough to be cut with a knife. Cerium is the second element in the lanthanide series, and while it often shows the +3 oxidation state characteristic of the series, it also exceptionally has a stable +4 state that does not oxidize water. It is also considered one of the rare-earth elements. Cerium has no biological role and is not very toxic.
Disulfur dioxide, dimeric sulfur monoxide or SO dimer is an oxide of sulfur. The solid is unstable with a lifetime of a few seconds at room temperature.
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