"plants, the calcium in mollusc shells, or the iron in the hemoglobin in vertebrate animals' red blood cells. The concept of an ""element"" as an undivisible substance has developed through three major historical phases: Classical definitions (such as those of the ancient Greeks), chemical definitions, and atomic definitions. Ancient philosophy posited a set of classical elements to explain observed patterns in nature. These ""elements"" originally referred to ""earth"", ""water"", ""air"" and ""fire"" rather than the chemical elements of modern science. The term 'elements' (""stoicheia"") was first used by the Greek philosopher Plato in about 360 BCE in his dialogue Timaeus,"
"FeS, Fe(CO), FeF, FeI, Fe(ONap), Fe(NO), Fe(CO), FeCO, FeO, FeO, FeO, Fe(CO), Fe(ClO), FePO, (NHSO)Fe, FeSO, Fe(SO), FeS Kr, KrF, add Krypton compounds here LaB, La(CO), LaCl, LaF, LaO, La(NO), LaPO, La(SO) Lr, add Lawrencium compounds here PbCO, PbCl, PbCl, PbO, PbF, PbI, Pb(CH), Pb(CH), Pb(NO), PbO, PbSO, PbS, PbSe, PbTe. LiH, LiN, LiNH, LiO, LiOH, LiF, LiCl, LiBr, LiI, LiCO, LiSO LuBr, Lu(CO), LuCl, LuF, LuI, Lu(NO), LuO, LuPO, Lu(SO), LuS Mg(HCO), MgB, MgBr, MgC, MgCO, MgCl, Magnesium citrate, MgNCN, MgF, MgPOF, Mg(HOCH(CHOH)CO), MgH, MgHPO, Mg(OH), Mg(OCl), MgI, MgMoO, Mg(NO), MgCO, MgO, MgO, Mg(PO), MgSiO, MgSO, MgS, MgTiO, MgWO,"
"FeMoco FeMoco ( cofactor) is the primary cofactor of nitrogenase. Nitrogenase is the enzyme that catalyzes the conversion of atmospheric nitrogen molecules N into ammonia (NH) through the process known as nitrogen fixation. Containing iron and molybdenum, the cofactor is called FeMoco. Its stoichiometry is FeMoSC. The FeMo cofactor is a cluster with composition FeMoSC. Fe is the chemical symbol for the element iron (ferrum), and Mo is the symbol for molybdenum. This large cluster can be viewed as two subunits composed of one FeS (iron(III) sulfide) cluster and one MoFeS cluster. The two clusters are linked by three sulfide"
"Germanium Germanium is a chemical element with symbol Ge and atomic number 32. It is a lustrous, hard, grayish-white metalloid in the carbon group, chemically similar to its group neighbors tin and silicon. Pure germanium is a semiconductor with an appearance similar to elemental silicon. Like silicon, germanium naturally reacts and forms complexes with oxygen in nature. Because it seldom appears in high concentration, germanium was discovered comparatively late in the history of chemistry. Germanium ranks near fiftieth in relative abundance of the elements in the Earth's crust. In 1869, Dmitri Mendeleev predicted its existence and some of its properties"
"In the cluster FeBr the cation Fe stands for [FeO(OH)(tacn)], with tacn representing 1,4,7-triazacyclononane. The ferrous cube complex FeCHNO (commonly called [Fe(sae)(MeOH)]) was the first example of a single-molecule magnet involving an Fe(II) cluster, and the core of this complex is a slightly distorted cube with Fe and O atoms on alternating corners. Remarkably, this single-molecule magnet exhibits non-collinear magnetism, in which the atomic spin moments of the four Fe atoms point in opposite directions along two nearly perpendicular axes. Theoretical computations showed that approximately two magnetic electrons are localized on each Fe atom, with the other atoms being nearly"
"Fermium Fermium is a synthetic element with symbol Fm and atomic number 100. It is an actinide and the heaviest element that can be formed by neutron bombardment of lighter elements, and hence the last element that can be prepared in macroscopic quantities, although pure fermium metal has not yet been prepared. A total of 19 isotopes are known, with Fm being the longest-lived with a half-life of 100.5 days. It was discovered in the debris of the first hydrogen bomb explosion in 1952, and named after Enrico Fermi, one of the pioneers of nuclear physics. Its chemistry is typical"
"Iron–nickel alloy An iron–nickel alloy or nickel–iron alloy, abbreviated FeNi or NiFe, is a group of alloys consisting primarily of the elements nickel (Ni) and iron (Fe). It is the main constituent of the ""iron"" planetary cores and iron meteorites. The acronym NiFe refers to various chemical reactions that involve an iron–nickel catalyst or component, or in geology, to the general composition of planetary cores (including Earth's). Some iron–nickel alloys are called nickel steel and usually contain additional elements, depending on the purpose. Iron and nickel are notable for being the final elements produced by stellar nucleosynthesis, and the heaviest"
"performance of FeO using nanostructuring, surface functionalization, or by employing alternate crystal phases such as β-FeO. A mixture of zinc oxide with about 0.5% iron(III) oxide is called calamine, which is the active ingredient of calamine lotion. Iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula FeO. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare, and iron(II,III) oxide (FeO), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, FeO is the main source of iron for the steel"
"window – not obstruct or detract from window detail. Iron - chemical symbol FE - the most commonly occurring (by weight) element on earth is, at the same time, the rarest in its elemental form. While the magma core of the earth is made mostly of iron and the red hills of the Rockies and brown and gold fieldstone all contain iron, the iron exists only in its various oxide forms. The only naturally occurring pure iron is found in fresh meteorites (and some very rare chemical situations - like bog iron in the New Jersey cedar swamps). Meteorites quickly"
"Potassium ferrate Potassium ferrate is the chemical compound with the formula KFeO. This purple salt is paramagnetic, and is a rare example of an iron(VI) compound. In most of its compounds, iron has the oxidation state +2 or +3 (Fe or Fe). Reflecting its high oxidation state, FeO is a powerful oxidizing agent. Georg Ernst Stahl (1660 – 1734) first discovered that the residue formed by igniting a mixture of potassium nitrate (saltpetre) and iron powder dissolved in water to give a purple solution. Edmond Frémy (1814 – 1894) later discovered that fusion of potassium hydroxide and iron(III) oxide in"
"Symbol (chemistry) In relation to the chemical elements, a symbol is a code for a chemical element. Many functional groups have their own chemical symbol, e.g. Ph for the phenyl group, and Me for the methyl group. Chemical symbols for elements normally consist of one or two letters from the Latin alphabet, but can contain three when the element has a systematic temporary name (as of March 2017, no discovered elements have such a name), and are written with the first letter capitalized. Earlier chemical element symbols stem from classical Latin and Greek vocabulary. For some elements, this is because"
"Fluorine Fluorine is a chemical element with symbol F and atomic number 9. It is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. As the most electronegative element, it is extremely reactive, as it reacts with almost all other elements, except for helium and neon. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the"
"Phenylalanine Phenylalanine (symbol Phe or F) is an essential α-amino acid with the formula . It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert and hydrophobic nature of the benzyl side chain. The -isomer is used to biochemically form proteins, coded for by DNA. Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and the skin pigment melanin. It is encoded by"
"grams. The ""atomic mass"" of the Fe isotope is 55.935 u and one mole of Fe atoms would then in theory have a mass of 55.935 g, but such amounts of pure Fe have never been found (or separated out) on Earth. However, there are 22 mononuclidic elements of which essentially only a single isotope is found in nature (common examples are fluorine, sodium, aluminum and phosphorus) and for these elements the standard atomic weight and atomic mass are the same. Samples of these elements therefore may serve as reference standards for certain atomic mass values. The formula used for"
"Ferroin Ferroin is the chemical compound with the formula [Fe(""o""-phen)]SO, where ""o""-phen is an abbreviation for 1,10-phenanthroline, a bidentate ligand. The term ""ferroin"" is used loosely and includes salts of other anions such as chloride. This coordination compound is used as an indicator in analytical chemistry. The active ingredient is the [Fe(""o""-phen)] ion, which is a chromophore that can be oxidized to the ferric derivative [Fe(""o""-phen)]. The potential for this redox change is +1.06 volts in 1 M HSO. It is a popular redox indicator for making oscillatory Belousov–Zhabotinsky reactions visible. Ferroin is suitable as a redox indicator, as the"
"Ferricyanide Ferricyanide is the anion [Fe(CN)]. It is also called hexacyanoferrate(III) and in rare, but systematic nomenclature, hexacyanidoferrate(III). The most common salt of this anion is potassium ferricyanide, a red crystalline material that is used as an oxidant in organic chemistry. [Fe(CN)] consists of a Fe center bound in octahedral geometry to six cyanide ligands. The complex has O symmetry. The iron is low spin and easily reduced to the related ferrocyanide ion [Fe(CN)], which is a ferrous (Fe) derivative. This redox couple is reversible and entails no making or breaking of Fe-C bonds: This redox couple is a standard"
"with acetic anhydride yields acetylferrocene just as acylation of benzene yields acetophenone under similar conditions. Iron-centered organometallic species are used as catalysts. The Knölker complex, for example, is a transfer hydrogenation catalyst for ketones. As iron has been in use for such a long time, it has many different names in different languages. The source of its chemical symbol ""Fe"" is the Latin word ""ferrum"", and its descendants are the names of the element in the Romance languages (for example, French ""fer"", Spanish ""hierro"", and Italian and Portuguese ""ferro""). The word ""ferrum"" itself possibly comes from the Semitic languages, via"
"Francium Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium. It is extremely radioactive; its most stable isotope, francium-223 (originally called actinium K after the natural decay chain it appears in), has a half-life of only 22 minutes. It is the second-least electronegative element, behind only caesium, and is the second rarest naturally occurring element (after astatine). The isotopes of francium decay quickly into astatine, radium, and radon. As an alkali metal, it has one valence electron. Bulk francium has never been viewed. Because of the general appearance of the"
"Iron(II,III) oxide Iron(II,III) oxide is the chemical compound with formula FeO. It occurs in nature as the mineral magnetite. It is one of a number of iron oxides, the others being iron(II) oxide (FeO), which is rare, and iron(III) oxide (FeO) also known as hematite. It contains both Fe and Fe ions and is sometimes formulated as FeO ∙ FeO. This iron oxide is encountered in the laboratory as a black powder. It exhibits permanent magnetism and is ferrimagnetic, but is sometimes incorrectly described as ferromagnetic. Its most extensive use is as a black pigment. For this purpose, it is"
"Ammonium iron(III) sulfate Ammonium iron(III) sulfate, NHFe(SO)·12 HO, or NH[Fe(HO)](SO)·6 HO, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO) · 12 HO. It has the appearance of weakly violet, octahedrical crystals. There has been some discussion regarding the origin of the crystals' colour, with some ascribing it to impurities in the compound, and others claiming it to be a property of the crystal itself. FAS is paramagnetic, acidic and toxic towards microorganisms. It is a weak oxidizing agent, capable of"
"and health. Tellurium Tellurium is a chemical element with symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur. It is occasionally found in native form as elemental crystals. Tellurium is far more common in the universe as a whole than on Earth. Its extreme rarity in the Earth's crust, comparable to that of platinum, is due partly to its high atomic number, but also to its formation of a volatile hydride which caused it to be lost to space as a gas during the hot nebular"
"oxide and siliceous beryllium (ASTM D7458). Beryllium Beryllium is a chemical element with symbol Be and atomic number 4. It is a relatively rare element in the universe, usually occurring as a product of the spallation of larger atomic nuclei that have collided with cosmic rays. Within the cores of stars beryllium is depleted as it is fused and creates larger elements. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl (aquamarine, emerald) and chrysoberyl. As a free element it is a steel-gray, strong, lightweight and"
"Ununennium Ununennium, also known as eka-francium or simply element 119, is the hypothetical chemical element with symbol Uue and atomic number 119. ""Ununennium"" and ""Uue"" are the temporary systematic IUPAC name and symbol respectively, until a permanent name is decided upon. In the periodic table of the elements, it is expected to be an s-block element, an alkali metal, and the first element in the eighth period. It is the lightest element that has not yet been synthesized. Experiments aimed at the synthesis of ununennium began in December 2017 at RIKEN in Japan; another attempt by the team at the"
"Barium ferrite Barium ferrite, abbreviated BaFe, BaM, is the chemical compound with the formula BaFeO. This and related ferrite materials are components in magnetic stripe cards and loudspeaker magnets. BaFe is described as Ba(Fe)(O). The Fe centers are ferromagnetically coupled. This area of technology is usually considered to be an application of the related fields of materials science and solid state chemistry. Barium ferrite is a highly magnetic material, has a high packing density, and is a metal oxide. Studies of this material date at least as far back as 1931, and it has found applications in magnetic card strips,"
"of HAsSH. Analysis of classical oxidation states would recommend the description of arsenopyrite as Fe[AsS]. Iron-pyrite FeS represents the prototype compound of the crystallographic pyrite structure. The structure is simple cubic and was among the first crystal structures solved by X-ray diffraction. It belongs to the crystallographic space group ""Pa"" and is denoted by the Strukturbericht notation C2. Under thermodynamic standard conditions the lattice constant formula_1 of stoichiometric iron pyrite FeS amounts to . The unit cell is composed of a Fe face-centered cubic sublattice into which the S ions are embedded. The pyrite structure is also used by other"
"Hafnium 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. Hafnium is used in filaments and electrodes. Some semiconductor fabrication processes use its oxide for integrated circuits at 45 nm and smaller feature lengths. Some superalloys"
"a gas at standard conditions. The longer-lived flerovium isotope Fl has been considered of interest for future radiochemical studies. Flerovium Flerovium is a superheavy artificial chemical element with symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. The element is named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna, Russia, where the element was discovered in 1998. The name of the laboratory, in turn, honours the Russian physicist Georgy Flyorov ( in Cyrillic, hence the transliteration of ""yo"" to ""e""). The name was adopted by IUPAC on 30"
"Flerovium Flerovium is a superheavy artificial chemical element with symbol Fl and atomic number 114. It is an extremely radioactive synthetic element. The element is named after the Flerov Laboratory of Nuclear Reactions of the Joint Institute for Nuclear Research in Dubna, Russia, where the element was discovered in 1998. The name of the laboratory, in turn, honours the Russian physicist Georgy Flyorov ( in Cyrillic, hence the transliteration of ""yo"" to ""e""). The name was adopted by IUPAC on 30 May 2012. In the periodic table of the elements, it is a transactinide element in the p-block. It is"
"elements of the 7th period. Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K. It is one of the two least electronegative elements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. It was the last element discovered in nature, rather than by synthesis. Outside the laboratory, francium is extremely rare, with trace amounts"
"on the half-life of 3.1×10 years has been established. Fe is an extinct radionuclide of long half-life (2.6 million years). It is not found on Earth, but its ultimate decay product is its granddaughter, the stable nuclide Ni. Much of the past work on isotopic composition of iron has focused on the nucleosynthesis of Fe through studies of meteorites and ore formation. In the last decade, advances in mass spectrometry have allowed the detection and quantification of minute, naturally occurring variations in the ratios of the stable isotopes of iron. Much of this work is driven by the Earth and"
"Iron(III) nitrate Iron(III) nitrate, or ferric nitrate, is the chemical compound with the formula Fe(NO). Since it is deliquescent, it is commonly found in its nonahydrate form Fe(NO)·9HO in which it forms colourless to pale violet crystals. When dissolved, it forms yellow solution due to hydrolysis. The compound is prepared by treating iron metal powder with nitric acid. Ferric nitrate is the catalyst of choice for the synthesis of sodium amide from a solution of sodium in ammonia: Certain clays impregnated with ferric nitrate have been shown to be useful oxidants in organic synthesis. For example, ferric nitrate on Montmorillonite—a"
"(namely those in the actinium decay family, the radium decay family, and the thorium decay family) bear placeholder names using the early naming system devised by Ernest Rutherford. General: From organic chemistry: Exotic atoms: Symbol (chemistry) In relation to the chemical elements, a symbol is a code for a chemical element. Many functional groups have their own chemical symbol, e.g. Ph for the phenyl group, and Me for the methyl group. Chemical symbols for elements normally consist of one or two letters from the Latin alphabet, but can contain three when the element has a systematic temporary name (as of"
"Rutherfordium Rutherfordium is a synthetic chemical element with symbol Rf and atomic number 104, named after physicist Ernest Rutherford. As a synthetic element, it is not found in nature and can only be created in a laboratory. It is radioactive; the most stable known isotope, Rf, has a half-life of approximately 1.3 hours. In the periodic table of the elements, it is a d-block element and the second of the fourth-row transition elements. It is a member of the 7th period and belongs to the group 4 elements. Chemistry experiments have confirmed that rutherfordium behaves as the heavier homologue to"