Iridium is a chemical element; it has symbol Ir and atomic number 77. A very hard, brittle, silvery-white transition metal of the platinum group, it is considered the second-densest naturally occurring metal with a density of 22.56 g/cm3 (0.815 lb/cu in) as defined by experimental X-ray crystallography. 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. It is one of the most corrosion-resistant metals, even at temperatures as high as 2,000 °C (3,630 °F).
The mineral pyrite ( PY-ryte), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula FeS2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. Sulfide also refers to large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide.
Molybdenum disulfide is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is MoS
2.
Laurite is an opaque black, metallic ruthenium sulfide mineral with formula: RuS2. It crystallizes in the isometric system. It is in the pyrite structural group. Though it's been found in many localities worldwide, it is extremely rare.
A chalcogenide is a chemical compound consisting of at least one chalcogen anion and at least one more electropositive element. Although all group 16 elements of the periodic table are defined as chalcogens, the term chalcogenide is more commonly reserved for sulfides, selenides, tellurides, and polonides, rather than oxides. Many metal ores exist as chalcogenides. Photoconductive chalcogenide glasses are used in xerography. Some pigments and catalysts are also based on chalcogenides. The metal dichalcogenide MoS2 is a common solid lubricant.
Sulfur compounds are chemical compounds formed the element sulfur (S). Common oxidation states of sulfur range from −2 to +6. Sulfur forms stable compounds with all elements except the noble gases.
Copper monosulfide is a chemical compound of copper and sulfur. It was initially thought to occur in nature as the dark indigo blue mineral covellite. However, it was later shown to be rather a cuprous compound, formula Cu+3S(S2). CuS is a moderate conductor of electricity. A black colloidal precipitate of CuS is formed when hydrogen sulfide, H2S, is bubbled through solutions of Cu(II) salts. It is one of a number of binary compounds of copper and sulfur (see copper sulfide for an overview of this subject), and has attracted interest because of its potential uses in catalysis and photovoltaics.
Hydrodesulfurization (HDS), also called hydrotreatment or hydrotreating, is a catalytic chemical process widely used to remove sulfur (S) from natural gas and from refined petroleum products, such as gasoline or petrol, jet fuel, kerosene, diesel fuel, and fuel oils. The purpose of removing the sulfur, and creating products such as ultra-low-sulfur diesel, is to reduce the sulfur dioxide emissions that result from using those fuels in automotive vehicles, aircraft, railroad locomotives, ships, gas or oil burning power plants, residential and industrial furnaces, and other forms of fuel combustion.
In chemistry, the lattice energy is the energy change upon formation of one mole of a crystalline ionic compound from its constituent ions, which are assumed to initially be in the gaseous state. It is a measure of the cohesive forces that bind ionic solids. The size of the lattice energy is connected to many other physical properties including solubility, hardness, and volatility. Since it generally cannot be measured directly, the lattice energy is usually deduced from experimental data via the Born–Haber cycle.
Silicon disulfide is the inorganic compound with the formula SiS2. Like silicon dioxide, this material is polymeric, but it adopts a 1-dimensional structure quite different from the usual forms of SiO2.
Tin(IV) sulfide is a compound with the formula Sn S
2. The compound crystallizes in the cadmium iodide motif, with the Sn(IV) situated in "octahedral holes' defined by six sulfide centers. It occurs naturally as the rare mineral berndtite. It is useful as semiconductor material with band gap 2.2 eV.
The roughskin dogfish is a sleeper shark of the family Somniosidae, found around the world on continental shelves in tropical, subtropical and temperate seas, at depths of between 100 and 1,500 m. It reaches a length of 121 cm.
Tetrairidium dodecacarbonyl is the chemical compound with the formula Ir4(CO)12. This tetrahedral cluster is the most common and most stable "binary" carbonyl of iridium. This air-stable species is only poorly soluble in organic solvents. It has been used to prepare bimetallic clusters and catalysts, e.g. for the water gas shift reaction, and reforming, but these studies are of purely academic interest.
Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.
Cobalt sulfide is the name for chemical compounds with a formula CoxSy. Well-characterized species include minerals with the formulas CoS, CoS2, Co3S4, and Co9S8. In general, the sulfides of cobalt are black, semiconducting, insoluble in water, and nonstoichiometric.
North Macedonia is a member state of the North Atlantic Treaty Organization (NATO). In 1995, the country joined the Partnership for Peace. It then began taking part in various NATO missions, including the International Security Assistance Force and the Resolute Support Mission in Afghanistan. At the 2008 Bucharest summit, Greece vetoed the country's invitation to join; however, NATO member states agreed that the country would receive an invitation upon resolution of the Macedonia naming dispute. Following an agreement in June 2018 to rename the country, representatives of NATO member states signed a protocol on the accession of North Macedonia to NATO on 6 February 2019. Over the next thirteen months, all of NATO's 29 member states ratified the protocol. The accession protocol entered into force on 19 March 2020, allowing North Macedonia to deposit its instrument of accession and thereby become NATO's 30th member state on 27 March 2020.
Titanium disulfide is an inorganic compound with the formula TiS2. A golden yellow solid with high electrical conductivity, it belongs to a group of compounds called transition metal dichalcogenides, which consist of the stoichiometry ME2. TiS2 has been employed as a cathode material in rechargeable batteries.
Rhenium disulfide is an inorganic compound of rhenium and sulfur with the formula ReS2. It has a layered structure where atoms are strongly bonded within each layer. The layers are held together by weak Van der Waals bonds, and can be easily peeled off from the bulk material.
Iridium compounds are compounds containing the element iridium (Ir). Iridium forms compounds in oxidation states between −3 and +9, but the most common oxidation states are +1, +2, +3, and +4. Well-characterized compounds containing iridium in the +6 oxidation state include IrF6 and the oxides Sr2MgIrO6 and Sr2CaIrO6. iridium(VIII) oxide was generated under matrix isolation conditions at 6 K in argon. The highest oxidation state (+9), which is also the highest recorded for any element, is found in gaseous [IrO4]+.
