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115-495: Water that flows from the Askam Borehole contains a significant amount of iron deposits. Upon exposure to air, the iron precipitates in the form of iron hydroxide , a reddish-orange compound that coats stream channels . The borehole contributes pollution to Nanticoke Creek. In the 1970s, an Operation Scarlift report found the concentration of acidity in the discharges of the Askam Borehole to be 633 parts per million and

230-434: A body-centered cubic (bcc) crystal structure . As it cools further to 1394 °C, it changes to its γ-iron allotrope, a face-centered cubic (fcc) crystal structure, or austenite . At 912 °C and below, the crystal structure again becomes the bcc α-iron allotrope. The physical properties of iron at very high pressures and temperatures have also been studied extensively, because of their relevance to theories about

345-430: A nuclear spin (− 1 ⁄ 2 ). The nuclide Fe theoretically can undergo double electron capture to Cr, but the process has never been observed and only a lower limit on the half-life of 4.4×10 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

460-738: 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

575-499: A supernova for their formation, involving rapid neutron capture by starting Fe nuclei. In the far future of the universe, assuming that proton decay does not occur, cold fusion occurring via quantum tunnelling would cause the light nuclei in ordinary matter to fuse into Fe nuclei. Fission and alpha-particle emission would then make heavy nuclei decay into iron, converting all stellar-mass objects to cold spheres of pure iron. Iron's abundance in rocky planets like Earth

690-540: A considerable amount of time. (See element naming controversy ). Precursors of such controversies involved the nationalistic namings of elements in the late 19th century. For example, lutetium was named in reference to Paris, France. The Germans were reluctant to relinquish naming rights to the French, often calling it cassiopeium . Similarly, the British discoverer of niobium originally named it columbium , in reference to

805-432: A deep violet complex: 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 the same element can have different numbers of neutrons in their nuclei, known as isotopes of

920-477: 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"

1035-454: A distorted sodium chloride structure. The binary ferrous and ferric halides are well-known. The ferrous halides typically arise from treating iron metal with the corresponding hydrohalic acid to give the corresponding hydrated salts. Iron reacts with fluorine, chlorine, and bromine to give the corresponding ferric halides, ferric chloride being the most common. Ferric iodide is an exception, being thermodynamically unstable due to

1150-643: A few decay products, to have been differentiated from other elements. Most recently, the synthesis of element 118 (since named oganesson ) was reported in October 2006, and the synthesis of element 117 ( tennessine ) was reported in April 2010. Of these 118 elements, 94 occur naturally on Earth. Six of these occur in extreme trace quantities: technetium , atomic number 43; promethium , number 61; astatine , number 85; francium , number 87; neptunium , number 93; and plutonium , number 94. These 94 elements have been detected in

1265-525: A few elements, such as silver and gold , are found uncombined as relatively pure native element minerals . Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is mostly a mixture of molecular nitrogen and oxygen , though it does contain compounds including carbon dioxide and water , as well as atomic argon , a noble gas which is chemically inert and therefore does not undergo chemical reactions. The history of

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1380-553: A macroscopic piece of iron will have a nearly zero overall magnetic field. Application of an external magnetic field causes the domains that are magnetized in the same general direction to grow at the expense of adjacent ones that point in other directions, reinforcing the external field. This effect is exploited in devices that need to channel magnetic fields to fulfill design function, such as electrical transformers , magnetic recording heads, and electric motors . Impurities, lattice defects , or grain and particle boundaries can "pin"

1495-475: A mixture of O 2 /Ar. Iron(IV) is a common intermediate in many biochemical oxidation reactions. Numerous organoiron compounds contain formal oxidation states of +1, 0, −1, or even −2. The oxidation states and other bonding properties are often assessed using the technique of Mössbauer spectroscopy . Many mixed valence compounds contain both iron(II) and iron(III) centers, such as magnetite and Prussian blue ( Fe 4 (Fe[CN] 6 ) 3 ). The latter

1610-500: 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

1725-483: 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)

1840-471: A result, mercury is traded in standardized 76 pound flasks (34 kg) made of iron. Iron is by far the most reactive element in its group; it is pyrophoric when finely divided and dissolves easily in dilute acids, giving Fe . However, it does not react with concentrated nitric acid and other oxidizing acids due to the formation of an impervious oxide layer, which can nevertheless react with hydrochloric acid . High-purity iron, called electrolytic iron ,

1955-456: 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

2070-455: A type of rock consisting of repeated thin layers of iron oxides alternating with bands of iron-poor shale and chert . The banded iron formations were laid down in the time between 3,700  million years ago and 1,800  million years ago . Materials containing finely ground iron(III) oxides or oxide-hydroxides, such as ochre , have been used as yellow, red, and brown pigments since pre-historical times. They contribute as well to

2185-435: A very large coordination and organometallic chemistry : indeed, it was the discovery of an iron compound, ferrocene , that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d 4s , of which

2300-474: 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

2415-404: 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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2530-606: 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

2645-406: 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

2760-630: Is also rarely found in basalts that have formed from magmas that have come into contact with carbon-rich sedimentary rocks, which have reduced the oxygen fugacity sufficiently for iron to crystallize. This is known as telluric iron and is described from a few localities, such as Disko Island in West Greenland, Yakutia in Russia and Bühl in Germany. Ferropericlase (Mg,Fe)O , a solid solution of periclase (MgO) and wüstite (FeO), makes up about 20% of

2875-812: 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

2990-460: 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

3105-407: Is considered to be resistant to rust, due to its oxide layer. Iron forms various oxide and hydroxide compounds ; the most common are iron(II,III) oxide (Fe 3 O 4 ), and iron(III) oxide (Fe 2 O 3 ). Iron(II) oxide also exists, though it is unstable at room temperature. Despite their names, they are actually all non-stoichiometric compounds whose compositions may vary. These oxides are

3220-495: Is due to its abundant production during the runaway fusion and explosion of type Ia supernovae , which scatters the iron into space. Metallic or native iron is rarely found on the surface of the Earth because it tends to oxidize. However, both the Earth's inner and outer core , which together account for 35% of the mass of the whole Earth, are believed to consist largely of an iron alloy, possibly with nickel . Electric currents in

3335-474: Is experimentally well defined for pressures less than 50 GPa. For greater pressures, published data (as of 2007) still varies by tens of gigapascals and over a thousand kelvin. Below its Curie point of 770 °C (1,420 °F; 1,040 K), α-iron changes from paramagnetic to ferromagnetic : the spins of the two unpaired electrons in each atom generally align with the spins of its neighbors, creating an overall magnetic field . This happens because

3450-443: Is in Earth's crust only amounts to about 5% of the overall mass of the crust and is thus only the fourth most abundant element in that layer (after oxygen , silicon , and aluminium ). Most of the iron in the crust is combined with various other elements to form many iron minerals . An important class is the iron oxide minerals such as hematite (Fe 2 O 3 ), magnetite (Fe 3 O 4 ), and siderite (FeCO 3 ), which are

3565-401: Is not like that of Mn with its weak, spin-forbidden d–d bands, because Fe has higher positive charge and is more polarizing, lowering the energy of its ligand-to-metal charge transfer absorptions. Thus, all the above complexes are rather strongly colored, with the single exception of the hexaquo ion – and even that has a spectrum dominated by charge transfer in the near ultraviolet region. On

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3680-436: 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

3795-407: Is possible, but nonetheless the sequence does effectively end at Ni because conditions in stellar interiors cause the competition between photodisintegration and the alpha process to favor photodisintegration around Ni. This Ni, which has a half-life of about 6 days, is created in quantity in these stars, but soon decays by two successive positron emissions within supernova decay products in

3910-548: Is somewhat different). Pieces of magnetite with natural permanent magnetization ( lodestones ) provided the earliest compasses for navigation. Particles of magnetite were extensively used in magnetic recording media such as core memories , magnetic tapes , floppies , and disks , until they were replaced by cobalt -based materials. Iron has four stable isotopes : Fe (5.845% of natural iron), Fe (91.754%), Fe (2.119%) and Fe (0.282%). Twenty-four artificial isotopes have also been created. Of these stable isotopes, only Fe has

4025-442: Is such a strong oxidizing agent that it oxidizes ammonia to nitrogen (N 2 ) and water to oxygen: The pale-violet hex aquo complex [Fe(H 2 O) 6 ] is an acid such that above pH 0 it is fully hydrolyzed: As pH rises above 0 the above yellow hydrolyzed species form and as it rises above 2–3, reddish-brown hydrous iron(III) oxide precipitates out of solution. Although Fe has a d configuration, its absorption spectrum

4140-502: Is supposed to have an orthorhombic or a double hcp structure. (Confusingly, the term "β-iron" is sometimes also used to refer to α-iron above its Curie point, when it changes from being ferromagnetic to paramagnetic, even though its crystal structure has not changed. ) The inner core of the Earth is generally presumed to consist of an iron- nickel alloy with ε (or β) structure. The melting and boiling points of iron, along with its enthalpy of atomization , are lower than those of

4255-426: 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

4370-581: Is the only source of water for the lower reaches of Nanticoke Creek. It discharges in two different locations. The Askam Borehole is named after Askam , a nearby village. It was drilled in the early 1970s by the Pennsylvania Department of Environmental Resources (later known as the Pennsylvania Department of Environmental Protection ). The borehole was created for the purpose of alleviating water pressure from an underground mine pool that

4485-418: Is thus very important economically, and iron is the cheapest metal, with a price of a few dollars per kilogram or pound. Pristine and smooth pure iron surfaces are a mirror-like silvery-gray. Iron reacts readily with oxygen and water to produce brown-to-black hydrated iron oxides , commonly known as rust . Unlike the oxides of some other metals that form passivating layers, rust occupies more volume than

4600-532: 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

4715-451: Is used as the traditional "blue" in blueprints . Iron is the first of the transition metals that cannot reach its group oxidation state of +8, although its heavier congeners ruthenium and osmium can, with ruthenium having more difficulty than osmium. Ruthenium exhibits an aqueous cationic chemistry in its low oxidation states similar to that of iron, but osmium does not, favoring high oxidation states in which it forms anionic complexes. In

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4830-437: Is used in chemical actinometry and along with its sodium salt undergoes photoreduction applied in old-style photographic processes. The dihydrate of iron(II) oxalate has a polymeric structure with co-planar oxalate ions bridging between iron centres with the water of crystallisation located forming the caps of each octahedron, as illustrated below. Iron(III) complexes are quite similar to those of chromium (III) with

4945-417: 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

5060-429: 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

5175-585: Is widely used. For example, the French chemical terminology distinguishes élément chimique (kind of atoms) and corps simple (chemical substance consisting of a single kind of atoms); the Russian chemical terminology distinguishes химический элемент and простое вещество . Almost all baryonic matter in the universe is composed of elements (among rare exceptions are neutron stars ). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds . Only

5290-557: The 2nd millennium BC and the use of iron tools and weapons began to displace copper alloys – in some regions, only around 1200 BC. That event is considered the transition from the Bronze Age to the Iron Age . In the modern world , iron alloys, such as steel , stainless steel , cast iron and special steels , are by far the most common industrial metals, due to their mechanical properties and low cost. The iron and steel industry

5405-480: The International Union of Pure and Applied Chemistry (IUPAC) had recognized a total of 118 elements. The first 94 occur naturally on Earth , and the remaining 24 are synthetic elements produced in nuclear reactions. Save for unstable radioactive elements (radioelements) which decay quickly, nearly all elements are available industrially in varying amounts. The discovery and synthesis of further new elements

5520-625: The Latin alphabet are likely to use the IUPAC element names. According to IUPAC, element names are not proper nouns; therefore, the full name of an element is not capitalized in English, even if derived from a proper noun , as in californium and einsteinium . Isotope names are also uncapitalized if written out, e.g., carbon-12 or uranium-235 . Chemical element symbols (such as Cf for californium and Es for einsteinium), are always capitalized (see below). In

5635-423: 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

5750-525: The most common element on Earth , forming much of Earth's outer and inner core . It is the fourth most abundant element in the Earth's crust , being mainly deposited by meteorites in its metallic state. Extracting usable metal from iron ores requires kilns or furnaces capable of reaching 1,500 °C (2,730 °F), about 500 °C (932 °F) higher than that required to smelt copper . Humans started to master that process in Eurasia during

5865-405: 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

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5980-418: The pH was measured to be 3.7. The concentration of iron was 384 parts per million and the sulfate concentration was 1936 parts per million. The daily load of acidity was found to be 29,100 pounds (13,200 kg) and the daily load of iron was 17,660 pounds (8,010 kg). The Askam Borehole discharges 3,500 US gallons (13 m) of acid mine drainage per minute into Nanticoke Creek. The discharge of

6095-432: The supernova remnant gas cloud, first to radioactive Co, and then to stable Fe. As such, iron is the most abundant element in the core of red giants , and is the most abundant metal in iron meteorites and in the dense metal cores of planets such as Earth . It is also very common in the universe, relative to other stable metals of approximately the same atomic weight . Iron is the sixth most abundant element in

6210-488: The trans - chlorohydridobis(bis-1,2-(diphenylphosphino)ethane)iron(II) complex is used as a starting material for compounds with the Fe( dppe ) 2 moiety . The ferrioxalate ion with three oxalate ligands displays helical chirality with its two non-superposable geometries labelled Λ (lambda) for the left-handed screw axis and Δ (delta) for the right-handed screw axis, in line with IUPAC conventions. Potassium ferrioxalate

6325-466: The universe , and the most common refractory element. Although a further tiny energy gain could be extracted by synthesizing Ni , which has a marginally higher binding energy than Fe, conditions in stars are unsuitable for this process. Element production in supernovas greatly favor iron over nickel, and in any case, Fe still has a lower mass per nucleon than Ni due to its higher fraction of lighter protons. Hence, elements heavier than iron require

6440-570: The 3d and 4s electrons are relatively close in energy, and thus a number of electrons can be ionized. Iron forms compounds mainly in the oxidation states +2 ( iron(II) , "ferrous") and +3 ( iron(III) , "ferric"). Iron also occurs in higher oxidation states , e.g., the purple potassium ferrate (K 2 FeO 4 ), which contains iron in its +6 oxidation state. The anion [FeO 4 ] with iron in its +7 oxidation state, along with an iron(V)-peroxo isomer, has been detected by infrared spectroscopy at 4 K after cocondensation of laser-ablated Fe atoms with

6555-638: 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

6670-622: The Askam Borehole. The treatment system makes use of a technology known as the Maelstrom Oxidizer, which uses electricity to blow air across the surface of the water, causing iron to precipitate from the water before the water is moved to a holding pond and then into the stream. The treatment system is known as the Askam AMD Treatment System or the Askam Treatment System. An artificial wetland has also been used to treat

6785-589: The Earth's surface. Items made of cold-worked meteoritic iron have been found in various archaeological sites dating from a time when iron smelting had not yet been developed; and the Inuit in Greenland have been reported to use iron from the Cape York meteorite for tools and hunting weapons. About 1 in 20 meteorites consist of the unique iron-nickel minerals taenite (35–80% iron) and kamacite (90–95% iron). Native iron

6900-487: 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

7015-487: 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,

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7130-466: The borehole can reach up to 7,000 US gallons (26 m) per minute during heavy rain. In the 1970s, an Operation Scarlift report found the discharge of the borehole to be 5.51 million gallons per day. The Askam Borehole is located in Hanover Township , in the central part of Luzerne County. The borehole is in the watershed of Nanticoke Creek, whose watershed has been deep mined and strip mined in

7245-629: The borehole's discharges. This wetland was constructed in May 1999 and has an area of 2.2 acres (0.89 ha). In the 2010s, the Earth Conservancy was awarded a $ 250,000 grant by the Pennsylvania Department of Environmental Protection to clean up the Askam Borehole discharges. There are plans for the Eastern Pennsylvania Coalition for Abandoned Mine Restoration to continue to take biological stream samples and water quality measurements in

7360-450: The brown deposits present in a sizeable number of streams. Due to its electronic structure, iron has a very large coordination and organometallic chemistry. Many coordination compounds of iron are known. A typical six-coordinate anion is hexachloroferrate(III), [FeCl 6 ] , found in the mixed salt tetrakis(methylammonium) hexachloroferrate(III) chloride . Complexes with multiple bidentate ligands have geometric isomers . For example,

7475-413: 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

7590-683: The color of various rocks and clays , including entire geological formations like the Painted Hills in Oregon and the Buntsandstein ("colored sandstone", British Bunter ). Through Eisensandstein (a jurassic 'iron sandstone', e.g. from Donzdorf in Germany) and Bath stone in the UK, iron compounds are responsible for the yellowish color of many historical buildings and sculptures. The proverbial red color of

7705-464: The cores of the Earth and other planets. Above approximately 10 GPa and temperatures of a few hundred kelvin or less, α-iron changes into another hexagonal close-packed (hcp) structure, which is also known as ε-iron . The higher-temperature γ-phase also changes into ε-iron, but does so at higher pressure. Some controversial experimental evidence exists for a stable β phase at pressures above 50 GPa and temperatures of at least 1500 K. It

7820-408: 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

7935-416: 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

8050-401: The domains in the new positions, so that the effect persists even after the external field is removed – thus turning the iron object into a (permanent) magnet . Similar behavior is exhibited by some iron compounds, such as the ferrites including the mineral magnetite , a crystalline form of the mixed iron(II,III) oxide Fe 3 O 4 (although the atomic-scale mechanism, ferrimagnetism ,

8165-479: The earlier 3d elements from scandium to chromium , showing the lessened contribution of the 3d electrons to metallic bonding as they are attracted more and more into the inert core by the nucleus; however, they are higher than the values for the previous element manganese because that element has a half-filled 3d sub-shell and consequently its d-electrons are not easily delocalized. This same trend appears for ruthenium but not osmium . The melting point of iron

8280-526: 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

8395-406: 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

8510-470: 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

8625-480: 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

8740-413: 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

8855-474: 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

8970-406: The exception of iron(III)'s preference for O -donor instead of N -donor ligands. The latter tend to be rather more unstable than iron(II) complexes and often dissociate in water. Many Fe–O complexes show intense colors and are used as tests for phenols or enols . For example, in the ferric chloride test , used to determine the presence of phenols, iron(III) chloride reacts with a phenol to form

9085-492: 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

9200-630: 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

9315-529: 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

9430-462: The global stock of iron in use in society is 2,200 kg per capita. More-developed countries differ in this respect from less-developed countries (7,000–14,000 vs 2,000 kg per capita). Ocean science demonstrated the role of the iron in the ancient seas in both marine biota and climate. Iron shows the characteristic chemical properties of the transition metals , namely the ability to form variable oxidation states differing by steps of one and

9545-431: 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

9660-399: 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

9775-543: The heavy elements before the formation of the Solar System. For example, at over 1.9 × 10 years, over a billion times longer than the estimated age of the universe, bismuth-209 has the longest known alpha decay half-life of any isotope. The last 24 elements (those beyond plutonium, element 94) undergo radioactive decay with short half-lives and cannot be produced as daughters of longer-lived elements, and thus are not known to occur in nature at all. 1 The properties of

9890-449: The liquid outer core are believed to be the origin of the Earth's magnetic field . The other terrestrial planets ( Mercury , Venus , and Mars ) as well as the Moon are believed to have a metallic core consisting mostly of iron. The M-type asteroids are also believed to be partly or mostly made of metallic iron alloy. The rare iron meteorites are the main form of natural metallic iron on

10005-446: The literature, this mineral phase of the lower mantle is also often called magnesiowüstite. Silicate perovskite may form up to 93% of the lower mantle, and the magnesium iron form, (Mg,Fe)SiO 3 , is considered to be the most abundant mineral in the Earth, making up 38% of its volume. While iron is the most abundant element on Earth, most of this iron is concentrated in the inner and outer cores. The fraction of iron that

10120-407: The major ores of iron . Many igneous rocks also contain the sulfide minerals pyrrhotite and pentlandite . During weathering , iron tends to leach from sulfide deposits as the sulfate and from silicate deposits as the bicarbonate. Both of these are oxidized in aqueous solution and precipitate in even mildly elevated pH as iron(III) oxide . Large deposits of iron are banded iron formations ,

10235-775: The metal and thus flakes off, exposing more fresh surfaces for corrosion. Chemically, the most common oxidation states of iron are iron(II) and iron(III) . Iron shares many properties of other transition metals, including the other group 8 elements , ruthenium and osmium . Iron forms compounds in a wide range of oxidation states , −4 to +7. Iron also forms many coordination compounds ; some of them, such as ferrocene , ferrioxalate , and Prussian blue have substantial industrial, medical, or research applications. The body of an adult human contains about 4 grams (0.005% body weight) of iron, mostly in hemoglobin and myoglobin . These two proteins play essential roles in oxygen transport by blood and oxygen storage in muscles . To maintain

10350-551: The meteorites Semarkona and Chervony Kut, a correlation between the concentration of Ni, the granddaughter of Fe, and the abundance of the stable iron isotopes provided evidence for the existence of Fe at the time of formation of the Solar System . Possibly the energy released by the decay of Fe, along with that released by Al , contributed to the remelting and differentiation of asteroids after their formation 4.6 billion years ago. The abundance of Ni present in extraterrestrial material may bring further insight into

10465-559: The necessary levels, human iron metabolism requires a minimum of iron in the diet. Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. At least four allotropes of iron (differing atom arrangements in the solid) are known, conventionally denoted α , γ , δ , and ε . The first three forms are observed at ordinary pressures. As molten iron cools past its freezing point of 1538 °C, it crystallizes into its δ allotrope, which has

10580-436: The orbitals of those two electrons (d z and d x − y ) do not point toward neighboring atoms in the lattice, and therefore are not involved in metallic bonding. In the absence of an external source of magnetic field, the atoms get spontaneously partitioned into magnetic domains , about 10 micrometers across, such that the atoms in each domain have parallel spins, but some domains have other orientations. Thus

10695-533: The origin and early history of the Solar System . The most abundant iron isotope Fe is of particular interest to nuclear scientists because it represents the most common endpoint of nucleosynthesis . Since Ni (14 alpha particles ) is easily produced from lighter nuclei in the alpha process in nuclear reactions in supernovae (see silicon burning process ), it is the endpoint of fusion chains inside extremely massive stars . Although adding more alpha particles

10810-444: The other hand, the pale green iron(II) hexaquo ion [Fe(H 2 O) 6 ] does not undergo appreciable hydrolysis. Carbon dioxide is not evolved when carbonate anions are added, which instead results in white iron(II) carbonate being precipitated out. In excess carbon dioxide this forms the slightly soluble bicarbonate, which occurs commonly in groundwater, but it oxidises quickly in air to form iron(III) oxide that accounts for

10925-581: The oxidizing power of Fe and the high reducing power of I : Ferric iodide, a black solid, is not stable in ordinary conditions, but can be prepared through the reaction of iron pentacarbonyl with iodine and carbon monoxide in the presence of hexane and light at the temperature of −20 °C, with oxygen and water excluded. Complexes of ferric iodide with some soft bases are known to be stable compounds. The standard reduction potentials in acidic aqueous solution for some common iron ions are given below: The red-purple tetrahedral ferrate (VI) anion

11040-497: 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 planetary science communities, although applications to biological and industrial systems are emerging. In phases of

11155-615: The past. The borehole is near Dundee Road and Pennsylvania Route 29 . The Askam Borehole is one of two major outlets for mine water from the South-East Mine Pool Complex , with the other being the South Wilkes-Barre Boreholes . The borehole itself has a diameter of 30 inches (76 cm). The Askam Borehole is the main point by which the T-B mine workings discharge acid mine drainage into Nanticoke Creek. The borehole

11270-418: 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

11385-426: 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,

11500-414: The principal ores for the production of iron (see bloomery and blast furnace). They are also used in the production of ferrites , useful magnetic storage media in computers, and pigments. The best known sulfide is iron pyrite (FeS 2 ), also known as fool's gold owing to its golden luster. It is not an iron(IV) compound, but is actually an iron(II) polysulfide containing Fe and S 2 ions in

11615-412: 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

11730-772: 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

11845-919: 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,

11960-495: 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

12075-404: 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

12190-457: 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

12305-437: The second half of the 3d transition series, vertical similarities down the groups compete with the horizontal similarities of iron with its neighbors cobalt and nickel in the periodic table, which are also ferromagnetic at room temperature and share similar chemistry. As such, iron, cobalt, and nickel are sometimes grouped together as the iron triad . Unlike many other metals, iron does not form amalgams with mercury . As

12420-547: The surface of Mars is derived from an iron oxide-rich regolith . Significant amounts of iron occur in the iron sulfide mineral pyrite (FeS 2 ), but it is difficult to extract iron from it and it is therefore not exploited. In fact, iron is so common that production generally focuses only on ores with very high quantities of it. According to the International Resource Panel 's Metal Stocks in Society report ,

12535-496: 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

12650-955: 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

12765-561: 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

12880-420: The vicinity of the Askam Borehole. 41°12′01″N 75°57′58″W  /  41.200145°N 75.96606°W  / 41.200145; -75.96606 Iron Iron is a chemical element ; it has the symbol Fe (from Latin ferrum  'iron') and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table . It is, by mass,

12995-455: The volume of the lower mantle of the Earth, which makes it the second most abundant mineral phase in that region after silicate perovskite (Mg,Fe)SiO 3 ; it also is the major host for iron in the lower mantle. At the bottom of the transition zone of the mantle, the reaction γ- (Mg,Fe) 2 [SiO 4 ] ↔ (Mg,Fe)[SiO 3 ] + (Mg,Fe)O transforms γ-olivine into a mixture of silicate perovskite and ferropericlase and vice versa. In

13110-528: 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,

13225-490: Was causing groundwater to flood local basements . In 1975, an Operation Scarlift report estimated that the cost of treating the borehole's discharge would be $ 1,011,600 per year in 1975 dollars. An active treatment system for the Askam Borehole was proposed by the Earth Conservancy by 2013. As of 2014, the Earth Conservancy has been constructing, testing, and monitoring an abandoned mine drainage treatment system at

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