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{{More citations needed|date=January 2010}}
The '''Goldschmidt classification''',<ref>
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|last= Goldschmidt|first= Victor
|title= The principles of distribution of chemical elements in minerals and rocks. The seventh Hugo Müller Lecture, delivered before the Chemical Society
|journal= [[Journal of the Chemical Society]]
|date= 17 March 1937
|pages= 655–673|doi= 10.1039/JR9370000655}}<!--|
</ref><ref name=Albarede>{{Cite book |last=Albarède |first=Francis |url=https://www.cambridge.org/core/product/identifier/9780511807435/type/book |title=Geochemistry: An Introduction |date=2009-06-25 |publisher=Cambridge University Press |isbn=978-0-521-88079-4 |edition=2 |doi=10.1017/cbo9780511807435.005}}</ref>
developed by [[Victor Goldschmidt]] (1888–1947), is a [[Geochemistry|geochemical classification]] which groups the [[chemical element]]s within the Earth according to their preferred host phases into lithophile ([[Rock (geology)|rock]]-loving), siderophile ([[iron]]-loving), chalcophile ([[sulfide ore]]-loving or [[chalcogen]]-loving), and atmophile (gas-loving) or volatile (the element, or a compound in which it occurs, is liquid or gaseous at ambient surface conditions).
Some elements have affinities to more than one phase. The main affinity is given in the table below and a discussion of each group follows that table.
{{Periodic table (Goldschmidt classification)}}
The trace radioactive elements (namely Tc, Pm, Po, At, Rn, Fr, Ra, Ac, Pa, Np, and Pu) are shown as synthetic, because their occurrence in nature is fleeting and is entirely dependent on their long-lived parents Th and U, and they are not very mobile. For instance, polonium's chemistry would predict it to be a chalcophile, but in actuality it tends to occur instead as a lithophile along with its parent uranium; even radon, which is a gas, does not usually have time to travel very far from the original uranium source before decaying. When needed, these elements are typically produced synthetically in nuclear reactors instead of using the tedious and laborious process of extraction from uranium ores.▼
==Lithophile elements==
Lithophile elements ({{ety|grc|''{{lang|grc|λῐ́θος}}'' ({{transl|grc|líthos}})|stone||''{{lang|grc|φίλος}}'' ({{transl|grc|phílos}})|dear, beloved}}) are those that remain on or close to the surface because they combine readily with oxygen, forming compounds that
Lithophile elements mainly consist of the highly reactive metals of the [[s-block|s-]] and [[f-block]]s. They also include a small number of reactive nonmetals, and the more reactive metals of the [[d-block]] such as [[titanium]], [[zirconium]] and [[vanadium
▲Lithophile elements are those that remain on or close to the surface because they combine readily with oxygen, forming compounds that do not sink into the core. The lithophile elements include:{{citation needed|date=December 2015}} [[Aluminium|Al]], [[Boron|B]], [[Barium|Ba]], [[Beryllium|Be]], [[Bromine|Br]], [[Calcium|Ca]], [[Chlorine|Cl]], [[Chromium|Cr]], [[Caesium|Cs]], [[Fluorine|F]], [[Iodine|I]], [[Hafnium|Hf]], [[Potassium|K]], [[Lithium|Li]], [[Magnesium|Mg]], [[Sodium|Na]], [[Niobium|Nb]], [[Oxygen|O]], [[Phosphorus|P]], [[Rubidium|Rb]], [[Scandium|Sc]], [[Silicon|Si]], [[Strontium|Sr]], [[Tantalum|Ta]], [[Thorium|Th]], [[Titanium|Ti]], [[Uranium|U]], [[Vanadium|V]], [[Yttrium|Y]], [[Zirconium|Zr]], [[Tungsten|W]] and the [[lanthanides]].
Most lithophile elements form very stable [[ion]]s with an [[electron configuration]] of a noble gas (sometimes with additional f-electrons). The few that do not, such as silicon, phosphorus and boron, form
▲Lithophile elements mainly consist of the highly reactive metals of the [[s-block|s-]] and [[f-block]]s. They also include a small number of reactive nonmetals, and the more reactive metals of the [[d-block]] such as titanium, zirconium and vanadium. Lithophile derives from "lithos" which means "rock", and "phile" which means "love".
Because of their strong affinity for oxygen, most lithophile elements are enriched in the Earth's crust relative to their abundance in the solar system. The most reactive s- and f-block metals, which form either saline or [[metallic hydrides]], are known to be extraordinarily enriched on Earth as a whole relative to their solar abundances. This is because during the earliest stages of the [[Earth's formation]], the
▲Most lithophile elements form very stable [[ion]]s with an electron configuration of a noble gas (sometimes with additional f-electrons). The few that do not, such as silicon, phosphorus and boron, form extremely strong covalent bonds with oxygen – often involving [[pi bond]]ing. Their strong affinity for oxygen causes lithophile elements to associate very strongly with silica, forming relatively low-density minerals that thus float to the crust. The more soluble minerals formed by the [[alkali metal]]s tend to concentrate in seawater or extremely arid regions where they can crystallise. The less soluble lithophile elements are concentrated on ancient continental shields where all soluble minerals have been weathered.
The nonmetallic lithophiles
▲Because of their strong affinity for oxygen, most lithophile elements are enriched in the Earth's crust relative to their abundance in the solar system. The most reactive s- and f-block metals, which form either saline or metallic hydrides, are known to be extraordinarily enriched on Earth as a whole relative to their solar abundances. This is because during the earliest stages of the Earth's formation the reaction that controlled the stable form of each chemical element was its ability to form compounds with hydrogen. Under these conditions, the s- and f-block metals were strongly enriched during the formation of the Earth. The most enriched elements are rubidium, strontium and barium, which between them account for over 50 percent by mass of all elements heavier than iron in the Earth's crust.
Several transition metals, including [[chromium]], [[molybdenum]], [[iron]] and [[manganese]], show ''both'' lithophile ''and'' siderophile characteristics and can be found in both these two layers. Although these metals form strong bonds with oxygen and are never found in the Earth's crust in the free state, metallic forms of these elements are thought very likely to exist in the core of the earth as relics from when the atmosphere did not contain oxygen. Like the "pure" siderophiles, these elements (except iron) are considerably depleted in the crust relative to their solar abundances.▼
▲The nonmetallic lithophiles – phosphorus and the [[halogen]]s – exist on Earth as ionic salts with s-block metals in [[pegmatite]]s and seawater. With the exception of fluorine, whose hydride forms [[hydrogen bond]]s and is therefore of relatively low volatility, these elements have had their concentrations on Earth significantly reduced through escape of volatile hydrides during the Earth's formation. Although they are present in the Earth's crust in concentrations quite close to their solar abundances, phosphorus and the heavier halogens are probably significantly depleted ''on Earth as a whole'' relative to their solar abundances.
Owing to their strong affinity for oxygen, lithophile metals, although they form the great bulk of the metallic elements in Earth's crust, were never available as free metals before the development of [[electrolysis]]. With this development, many lithophile metals are of considerable value as structural metals ([[magnesium]], [[aluminium]], [[titanium]], [[vanadium]]) or as [[reducing agents]] (
▲Several transition metals, including chromium, molybdenum, iron and manganese, show ''both'' lithophile ''and'' siderophile characteristics and can be found in both these two layers. Although these metals form strong bonds with oxygen and are never found in the Earth's crust in the free state, metallic forms of these elements are thought very likely to exist in the core of the earth as relics from when the atmosphere did not contain oxygen. Like the "pure" siderophiles, these elements (except iron) are considerably depleted in the crust relative to their solar abundances.
The non-metals phosphorus and the halogens were also not known to early chemists, though production of these elements is less difficult than of metallic lithophiles since electrolysis is required only with fluorine. Elemental [[chlorine]] is particularly important as an [[oxidizing agent]]
▲Owing to their strong affinity for oxygen, lithophile metals, although they form the great bulk of the metallic elements in Earth's crust, were never available as free metals before the development of [[electrolysis]]. With this development, many lithophile metals are of considerable value as structural metals (magnesium, aluminium, titanium, vanadium) or as reducing agents (sodium, magnesium, calcium). The process of [[smelting]] these metals is extremely energy-intensive. With emissions of [[greenhouse gas]]es suspected of contributing to [[climate change]], the use of these elements as industrial metals is called into question, despite the depletion of rarer and less reactive chalcophile metals leaving few substitutes.
▲The non-metals phosphorus and the halogens were also not known to early chemists, though production of these elements is less difficult than of metallic lithophiles since electrolysis is required only with fluorine. Elemental chlorine is particularly important as an [[oxidizing agent]] – usually being made by electrolysis of [[sodium chloride]].
==Siderophile elements==
{{Redirect|Siderophile|the bacteria|Siderophilic bacteria|the disease "siderophilia"|Iron overload}}
{{see also|Earth's inner core#Composition}}
[[File:Elemental abundances.svg|thumb|350px|alt=see text|Abundance ([[atom fraction]]) of the chemical elements in Earth's upper [[continental crust]] as a function of atomic number. The rarest elements in the crust (shown in yellow) are not the heaviest, but are rather the siderophile (iron-loving) elements in the Goldschmidt classification of elements. These have been depleted by being relocated
Siderophile
The siderophile elements include the highly siderophilic [[ruthenium]], [[rhodium]], [[palladium]], [[rhenium]], [[osmium]], [[iridium]], [[platinum]], and [[gold]], the moderately siderophilic [[cobalt]] and [[nickel]], in addition to the "disputed" elements mentioned earlier
Most siderophile elements have practically no affinity
Because they are so concentrated in the dense core, siderophile elements are known for their rarity in the Earth's crust. Most of them have always been known as [[precious metal]]s because of this. Iridium is the rarest transition metal occurring within the Earth's crust, with an [[abundance by mass]] of less than one part per billion. Mineable [[Deposition (geology)|deposits]] of [[precious metals]] usually form as a result of the [[erosion]] of [[ultramafic rock]]s, but are not highly concentrated even compared to their [[Abundance of elements in Earth's crust|crustal abundances]], which are typically several orders of magnitude below their solar abundances. However, because they are concentrated in the [[Earth's mantle]] and [[Earth's core]], siderophile elements are believed to be present in the Earth as a whole (including the core) in something approaching their solar abundances.
==Chalcophile elements==
The chalcophile elements
Chalcophile elements are those that remain on or close to the surface because they combine readily with [[sulfur]] and some other [[chalcogen]]s other than oxygen, forming compounds which
Because these sulfides are much denser than the silicate minerals formed by lithophile elements, chalcophile elements separated below the lithophiles at the time of the first crystallization of the Earth's crust. This has led to their depletion in the Earth's crust relative to their solar abundances, though because the minerals they form are nonmetallic, this depletion has not reached the levels found with siderophile elements.
However, because they formed volatile hydrides
The most metallic chalcophile elements (of the copper, zinc and boron groups) may mix to some degree with iron in the Earth's core. They are not likely to be depleted on Earth as a whole relative to their solar abundances since they do not form volatile hydrides. [[Zinc]] and [[gallium]] are somewhat "lithophile" in nature because they often occur in silicate or related minerals and form quite strong bonds with oxygen. Gallium, notably, is sourced mainly from [[bauxite]], an [[aluminum hydroxide]] ore in which gallium
Although no chalcophile element is of high abundance in the Earth's crust, chalcophile elements constitute the bulk of commercially important metals. This is because, whereas lithophile elements require energy-intensive electrolysis for extraction, chalcophiles can be easily extracted by
==Atmophile elements==
The atmophile elements
Atmophile elements (also called "[[Volatile (chemistry)|volatile elements]]") are defined as those that remain mostly on or above
Hydrogen, which occurs in
Because all atmophile elements are either gases or form volatile hydrides, atmophile elements are
[[Argon]] is the exception among the noble gases: it is the third-most abundant component of [[Earth's atmosphere|Earth's present-day atmosphere]] after nitrogen and oxygen, comprising {{approx|1%}}. [[Argon-40]] is a stable [[daughter nuclide|daughter]] of radioactive potassium-40, and argon is heavy enough to be gravitationally captured by the post-accretion Earth, so while the proto-Earth's primordial argon was mostly driven off, this [[radiogenic]] argon has accumulated over geologic time. This makes Earth's argon abundance substantially different from cosmic abundance ratios for argon, being enormously enriched in {{simple nuclide|Ar|40}}, while {{simple nuclide|Ar|36}} predominates cosmically.
==Trace and synthetic elements==
[[Synthetic elements]] are excluded from the classification, as they do not occur naturally.
Trace radioactive elements (namely Tc, Pm, Po, At, Rn, Fr, Ra, Ac, Pa, Np, Pu) are also treated as synthetic. Although these do occur in nature,<ref>{{cite book |last1=Yoshida |first1 = Zenko|first2 = Stephen G.|last2 = Johnson|first3 = Takaumi|last3 = Kimura|first4 = John R.|last4=Krsul|ref=Yoshida et al.|contribution = Neptunium|title = The Chemistry of the Actinide and Transactinide Elements|editor1-first = Lester R.|editor1-last = Morss|editor2-first = Norman M.|editor2-last = Edelstein|editor3-first = Jean|editor3-last = Fuger|edition = 3rd|date = 2006|volume = 3|publisher = Springer|location = Dordrecht, the Netherlands<!--|pages=703–4-->|pages = 699–812|url = http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|doi = 10.1007/1-4020-3598-5_6|archive-url=https://web.archive.org/web/20180117190715/http://radchem.nevada.edu/classes/rdch710/files/neptunium.pdf|archive-date=January 17, 2018|isbn = 978-1-4020-3555-5}}</ref><ref name = "Cigar">
{{cite journal
|journal = Geochimica et Cosmochimica Acta
|volume = 63|issue = 2|pages = 275–285
|date = 1999
|doi = 10.1016/S0016-7037(98)00282-8
|title = Nature's uncommon elements: plutonium and technetium
|first1 = David
|last1 = Curtis
|last2 = Fabryka-Martin |first2=June |last3=Paul |first3=Dixon |last4=Cramer|first4=Jan
|bibcode=1999GeCoA..63..275C
▲
==See also==
* [[Abundance of the chemical elements]]
* [[Victor Goldschmidt]]
* [[Goldschmidt
==References==
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==External links==
* [http://ruby.colorado.edu/~smyth/G30103.html Mineralogy notes 3] {{Webarchive|url=https://web.archive.org/web/20130329175220/http://ruby.colorado.edu/~smyth/G30103.html |date=2013-03-29 }}
* W. M. White. [http://www.imwa.info/white-geochemistry.html Geochemistry]. {{ISBN|978-0470656686}}; [http://www.imwa.info/geochemistry/Chapters/Chapter07.pdf Chapter 7.2]
{{DEFAULTSORT:Goldschmidt Classification}}
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[[Category:Geochemistry]]
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[[Category:Periodic table]]
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