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83-409: Khromtau has important Chromium deposits, which are currently exploited in underground mines by Kazchrome, a subsidiary of Eurasian Natural Resources Corporation (ENRC). Previously, Chromite ore was mined in open cast mines, which left enormous pits behind. The newly built mosque and the also new Russian orthodox church are juxtaposed on the main square of town. FC Gornyak soccer team played in

166-543: A pitch accent . In Modern Greek, all vowels and consonants are short. Many vowels and diphthongs once pronounced distinctly are pronounced as /i/ ( iotacism ). Some of the stops and glides in diphthongs have become fricatives , and the pitch accent has changed to a stress accent . Many of the changes took place in the Koine Greek period. The writing system of Modern Greek, however, does not reflect all pronunciation changes. The examples below represent Attic Greek in

249-750: A Cr-Cr quintuple bond (length 183.51(4) pm) has also been described. Extremely bulky monodentate ligands stabilize this compound by shielding the quintuple bond from further reactions. Chromium is the 21st most abundant element in Earth's crust with an average concentration of 100 ppm. Chromium compounds are found in the environment from the erosion of chromium-containing rocks, and can be redistributed by volcanic eruptions. Typical background concentrations of chromium in environmental media are: atmosphere <10 ng/m ; soil <500 mg/kg; vegetation <0.5 mg/kg; freshwater <10 μg/L; seawater <1 μg/L; sediment <80 mg/kg. Chromium

332-414: A change to less toxic chromium(III) compounds. The mineral crocoite (which is also lead chromate PbCrO 4 ) was used as a yellow pigment shortly after its discovery. After a synthesis method became available starting from the more abundant chromite, chrome yellow was, together with cadmium yellow , one of the most used yellow pigments. The pigment does not photodegrade, but it tends to darken due to

415-525: A critical material during the emergency". The United States likewise considered chromium "essential for the German war industry" and made intense diplomatic efforts to keep it out of the hands of Nazi Germany . The high hardness and corrosion resistance of unalloyed chromium makes it a reliable metal for surface coating; it is still the most popular metal for sheet coating, with its above-average durability, compared to other coating metals. A layer of chromium

498-525: A fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Regarding the speech of the ancient Macedonians diverse theories have been put forward, but the epigraphic activity and the archaeological discoveries in the Greek region of Macedonia during the last decades has brought to light documents, among which the first texts written in Macedonian , such as

581-414: A high infrared and visible light reflectance. Chromium metal in air is passivated : it forms a thin, protective surface layer of chromium oxide with the corundum structure. Passivation can be enhanced by short contact with oxidizing acids like nitric acid . Passivated chromium is stable against acids. Passivation can be removed with a strong reducing agent that destroys the protective oxide layer on

664-490: A larger chromite deposit was discovered near Baltimore , United States, which quickly met the demand for tanning salts much more adequately than the crocoite that had been used previously. This made the United States the largest producer of chromium products until the year 1848, when larger deposits of chromite were uncovered near the city of Bursa , Turkey. With the development of metallurgy and chemical industries in

747-550: A prefix /e-/, called the augment . This was probably originally a separate word, meaning something like "then", added because tenses in PIE had primarily aspectual meaning. The augment is added to the indicative of the aorist, imperfect, and pluperfect, but not to any of the other forms of the aorist (no other forms of the imperfect and pluperfect exist). The two kinds of augment in Greek are syllabic and quantitative. The syllabic augment

830-422: A solution of polyvinyl butyral . An 8% solution of phosphoric acid in solvent was added just before application. It was found that an easily oxidized alcohol was an essential ingredient. A thin layer of about 10–15 μm was applied, which turned from yellow to dark green when it was cured. There is still a question as to the correct mechanism. Chrome green is a mixture of Prussian blue and chrome yellow , while

913-542: A strong Northwest Greek influence, and can in some respects be considered a transitional dialect, as exemplified in the poems of the Boeotian poet Pindar who wrote in Doric with a small Aeolic admixture. Thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Pamphylian Greek , spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either

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996-510: A vowel or /n s r/ ; final stops were lost, as in γάλα "milk", compared with γάλακτος "of milk" (genitive). Ancient Greek of the classical period also differed in both the inventory and distribution of original PIE phonemes due to numerous sound changes, notably the following: The pronunciation of Ancient Greek was very different from that of Modern Greek . Ancient Greek had long and short vowels ; many diphthongs ; double and single consonants; voiced, voiceless, and aspirated stops ; and

1079-547: Is Cr with a half-life of 27.7 days. All of the remaining radioactive isotopes have half-lives that are less than 24 hours and the majority less than 1 minute. Chromium also has two metastable nuclear isomers . The primary decay mode before the most abundant stable isotope, Cr, is electron capture and the primary mode after is beta decay . Cr is the radiogenic decay product of Mn (half-life 3.74 million years). Chromium isotopes are typically collocated (and compounded) with manganese isotopes. This circumstance

1162-428: Is 125 nanoohm - meters . Chromium has a high specular reflection in comparison to other transition metals. In infrared , at 425  μm , chromium has a maximum reflectance of about 72%, reducing to a minimum of 62% at 750 μm before rising again to 90% at 4000 μm. When chromium is used in stainless steel alloys and polished , the specular reflection decreases with the inclusion of additional metals, yet

1245-409: Is 8.5, which means that it can scratch samples of quartz and topaz , but can be scratched by corundum . Chromium is highly resistant to tarnishing , which makes it useful as a metal that preserves its outermost layer from corroding , unlike other metals such as copper , magnesium , and aluminium . Chromium has a melting point of 1907 °C (3465 °F), which is relatively low compared to

1328-580: Is Cr(VI). Chromium minerals as pigments came to the attention of the west in the eighteenth century. On 26 July 1761, Johann Gottlob Lehmann found an orange-red mineral in the Beryozovskoye mines in the Ural Mountains which he named Siberian red lead . Though misidentified as a lead compound with selenium and iron components, the mineral was in fact crocoite with a formula of PbCrO 4 . In 1770, Peter Simon Pallas visited

1411-461: Is a "substance of very high concern" (SVHC). Gaseous chromium has a ground-state electron configuration of [ Ar ] 3d 4s . It is the first element in the periodic table whose configuration violates the Aufbau principle . Exceptions to the principle also occur later in the periodic table for elements such as copper , niobium and molybdenum . Chromium is the first element in the 3d series where

1494-483: Is a strong oxidizing agent. Compounds of chromium(V) are rather rare; the oxidation state +5 is only realized in few compounds but are intermediates in many reactions involving oxidations by chromate. The only binary compound is the volatile chromium(V) fluoride (CrF 5 ). This red solid has a melting point of 30 °C and a boiling point of 117 °C. It can be prepared by treating chromium metal with fluorine at 400 °C and 200 bar pressure. The peroxochromate(V)

1577-418: Is added to stems beginning with consonants, and simply prefixes e (stems beginning with r , however, add er ). The quantitative augment is added to stems beginning with vowels, and involves lengthening the vowel: Some verbs augment irregularly; the most common variation is e → ei . The irregularity can be explained diachronically by the loss of s between vowels, or that of the letter w , which affected

1660-451: Is another example of the +5 oxidation state. Potassium peroxochromate (K 3 [Cr(O 2 ) 4 ]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures. This red brown compound is stable at room temperature but decomposes spontaneously at 150–170 °C. Compounds of chromium(IV) are slightly more common than those of chromium(V). The tetrahalides, CrF 4 , CrCl 4 , and CrBr 4 , can be produced by treating

1743-401: Is composed of four stable isotopes ; Cr, Cr, Cr and Cr, with Cr being the most abundant (83.789% natural abundance ). Cr is observationally stable , as it is theoretically capable of decaying to Ti via double electron capture with a half-life of no less than 1.3 × 10 years. Twenty-five radioisotopes have been characterized, ranging from Cr to Cr; the most stable radioisotope

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1826-448: Is considered by some linguists to have been closely related to Greek . Among Indo-European branches with living descendants, Greek is often argued to have the closest genetic ties with Armenian (see also Graeco-Armenian ) and Indo-Iranian languages (see Graeco-Aryan ). Ancient Greek differs from Proto-Indo-European (PIE) and other Indo-European languages in certain ways. In phonotactics , ancient Greek words could end only in

1909-414: Is deposited on pretreated metallic surfaces by electroplating techniques. There are two deposition methods: thin, and thick. Thin deposition involves a layer of chromium below 1 μm thickness deposited by chrome plating , and is used for decorative surfaces. Thicker chromium layers are deposited if wear-resistant surfaces are needed. Both methods use acidic chromate or dichromate solutions. To prevent

1992-447: Is formed, which can be stabilized as an ether adduct CrO 5 ·OR 2 . Chromic acid has the hypothetical formula H 2 CrO 4 . It is a vaguely described chemical, despite many well-defined chromates and dichromates being known. The dark red chromium(VI) oxide CrO 3 , the acid anhydride of chromic acid, is sold industrially as "chromic acid". It can be produced by mixing sulfuric acid with dichromate and

2075-626: Is mined as chromite (FeCr 2 O 4 ) ore. About two-fifths of the chromite ores and concentrates in the world are produced in South Africa, about a third in Kazakhstan, while India, Russia, and Turkey are also substantial producers. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan and southern Africa. Although rare, deposits of native chromium exist. The Udachnaya Pipe in Russia produces samples of

2158-604: Is stable at neutral pH . Some other notable chromium(II) compounds include chromium(II) oxide CrO , and chromium(II) sulfate CrSO 4 . Many chromium(II) carboxylates are known. The red chromium(II) acetate (Cr 2 (O 2 CCH 3 ) 4 ) is somewhat famous. It features a Cr-Cr quadruple bond . A large number of chromium(III) compounds are known, such as chromium(III) nitrate , chromium(III) acetate , and chromium(III) oxide . Chromium(III) can be obtained by dissolving elemental chromium in acids like hydrochloric acid or sulfuric acid , but it can also be formed through

2241-576: Is still high in comparison with other alloys. Between 40% and 60% of the visible spectrum is reflected from polished stainless steel. The explanation on why chromium displays such a high turnout of reflected photon waves in general, especially the 90% in infrared, can be attributed to chromium's magnetic properties. Chromium has unique magnetic properties; it is the only elemental solid that shows antiferromagnetic ordering at room temperature and below. Above 38 °C, its magnetic ordering becomes paramagnetic . The antiferromagnetic properties, which cause

2324-449: Is then used to produce alloys such as stainless steel. Pure chromium metal is produced by a different process: roasting and leaching of chromite to separate it from iron, followed by reduction with carbon and then aluminium . Trivalent chromium (Cr(III)) occurs naturally in many foods and is sold as a dietary supplement , although there is insufficient evidence that dietary chromium provides nutritional benefit to people. In 2014,

2407-523: Is used where high temperature would normally cause carburization , oxidation or corrosion . Incoloy 800 "is capable of remaining stable and maintaining its austenitic structure even after long time exposures to high temperatures". Nichrome is used as resistance wire for heating elements in things like toasters and space heaters. These uses make chromium a strategic material . Consequently, during World War II, U.S. road engineers were instructed to avoid chromium in yellow road paint, as it "may become

2490-590: Is useful in isotope geology . Manganese-chromium isotope ratios reinforce the evidence from Al and Pd concerning the early history of the Solar System . Variations in Cr/ Cr and Mn/Cr ratios from several meteorites indicate an initial Mn/ Mn ratio that suggests Mn-Cr isotopic composition must result from in-situ decay of Mn in differentiated planetary bodies. Hence Cr provides additional evidence for nucleosynthetic processes immediately before coalescence of

2573-679: The Archaic or Epic period ( c.  800–500 BC ), and the Classical period ( c.  500–300 BC ). Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers . It has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance . This article primarily contains information about

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2656-606: The Epic and Classical periods of the language, which are the best-attested periods and considered most typical of Ancient Greek. From the Hellenistic period ( c.  300 BC ), Ancient Greek was followed by Koine Greek , which is regarded as a separate historical stage, though its earliest form closely resembles Attic Greek , and its latest form approaches Medieval Greek . There were several regional dialects of Ancient Greek; Attic Greek developed into Koine. Ancient Greek

2739-594: The European Food Safety Authority concluded that research on dietary chromium did not justify it to be recognized as an essential nutrient . While chromium metal and Cr(III) ions are considered non-toxic, chromate and its derivatives, often called " hexavalent chromium ", is toxic and carcinogenic . According to the European Chemicals Agency (ECHA), chromium trioxide that is used in industrial electroplating processes

2822-546: The Kazakhstan First Division . They are now defunct. The colours of the bandy team Gornyak are green and white. They played a test match against Akzhaiyk at Medeu before the 2011 Asian Winter Games, but have no adult team in league as they used to. [1] Nowadays young players is the focus. The town sent a bandy team to the Spartakiade 2009. Aktobe Region, made up by players from Khromtau, won

2905-501: The Pella curse tablet , as Hatzopoulos and other scholars note. Based on the conclusions drawn by several studies and findings such as Pella curse tablet , Emilio Crespo and other scholars suggest that ancient Macedonian was a Northwest Doric dialect , which shares isoglosses with its neighboring Thessalian dialects spoken in northeastern Thessaly . Some have also suggested an Aeolic Greek classification. The Lesbian dialect

2988-603: The epic poems , the Iliad and the Odyssey , and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects. The origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between

3071-501: The present , future , and imperfect are imperfective in aspect; the aorist , present perfect , pluperfect and future perfect are perfective in aspect. Most tenses display all four moods and three voices, although there is no future subjunctive or imperative. Also, there is no imperfect subjunctive, optative or imperative. The infinitives and participles correspond to the finite combinations of tense, aspect, and voice. The indicative of past tenses adds (conceptually, at least)

3154-422: The visible spectrum , and almost 90% of infrared light . The name of the element is derived from the Greek word χρῶμα, chrōma , meaning color , because many chromium compounds are intensely colored. Industrial production of chromium proceeds from chromite ore (mostly FeCr 2 O 4 ) to produce ferrochromium , an iron-chromium alloy, by means of aluminothermic or silicothermic reactions . Ferrochromium

3237-445: The 3d electrons start to sink into the core; they thus contribute less to metallic bonding , and hence the melting and boiling points and the enthalpy of atomisation of chromium are lower than those of the preceding element vanadium . Chromium(VI) is a strong oxidising agent in contrast to the molybdenum (VI) and tungsten (VI) oxides. Chromium is the third hardest element after carbon ( diamond ) and boron . Its Mohs hardness

3320-1031: The 5th century BC. Ancient pronunciation cannot be reconstructed with certainty, but Greek from the period is well documented, and there is little disagreement among linguists as to the general nature of the sounds that the letters represent. /oː/ raised to [uː] , probably by the 4th century BC. Greek, like all of the older Indo-European languages , is highly inflected. It is highly archaic in its preservation of Proto-Indo-European forms. In ancient Greek, nouns (including proper nouns) have five cases ( nominative , genitive , dative , accusative , and vocative ), three genders ( masculine , feminine , and neuter ), and three numbers (singular, dual , and plural ). Verbs have four moods ( indicative , imperative , subjunctive , and optative ) and three voices (active, middle, and passive ), as well as three persons (first, second, and third) and various other forms. Verbs are conjugated through seven combinations of tenses and aspect (generally simply called "tenses"):

3403-495: The Archaic period of ancient Greek (see Homeric Greek for more details): Μῆνιν ἄειδε, θεά, Πηληϊάδεω Ἀχιλῆος οὐλομένην, ἣ μυρί' Ἀχαιοῖς ἄλγε' ἔθηκε, πολλὰς δ' ἰφθίμους ψυχὰς Ἄϊδι προΐαψεν ἡρώων, αὐτοὺς δὲ ἑλώρια τεῦχε κύνεσσιν οἰωνοῖσί τε πᾶσι· Διὸς δ' ἐτελείετο βουλή· ἐξ οὗ δὴ τὰ πρῶτα διαστήτην ἐρίσαντε Ἀτρεΐδης τε ἄναξ ἀνδρῶν καὶ δῖος Ἀχιλλεύς. The beginning of Apology by Plato exemplifies Attic Greek from

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3486-601: The Cr-centered Keggin anion [α-CrW 12 O 40 ] . Chromium(III) hydroxide (Cr(OH) 3 ) is amphoteric , dissolving in acidic solutions to form [Cr(H 2 O) 6 ] , and in basic solutions to form [Cr(OH) 6 ] . It is dehydrated by heating to form the green chromium(III) oxide (Cr 2 O 3 ), a stable oxide with a crystal structure identical to that of corundum . Chromium(VI) compounds are oxidants at low or neutral pH. Chromate anions ( CrO 4 ) and dichromate (Cr 2 O 7 ) anions are

3569-545: The Dorians. The Greeks of this period believed there were three major divisions of all Greek people – Dorians, Aeolians, and Ionians (including Athenians), each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, and Cypriot, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for

3652-832: The Solar System. Cr has been posited as a proxy for atmospheric oxygen concentration. Chromium is a member of group 6 , of the transition metals . The +3 and +6 states occur most commonly within chromium compounds, followed by +2; charges of +1, +4 and +5 for chromium are rare, but do nevertheless occasionally exist. Many Cr(0) complexes are known. Bis(benzene)chromium and chromium hexacarbonyl are highlights in organochromium chemistry . Chromium(II) compounds are uncommon, in part because they readily oxidize to chromium(III) derivatives in air. Water-stable chromium(II) chloride CrCl 2 that can be made by reducing chromium(III) chloride with zinc. The resulting bright blue solution created from dissolving chromium(II) chloride

3735-612: The Spartakiade in 2013. [2] For the 2014-15 season, two youth teams were allowed to participate in the leagues of Sverdlovsk Oblast . [3] Two players from Khromtau, Sultan Kadyrzhanov [4] and Kuanysh Tiemiralin [5] has played in Kazakhstan's only professional club, Akzhaiyk [6] from Oral . Sultan was also part of the Kazakh team at the 2011 Asian Winter Games and his World Championship debut came in 2018. A national youth championship has been organised. [7] 2016 Gornyak won

3818-560: The Western world, the need for chromium increased. Chromium is also famous for its reflective, metallic luster when polished. It is used as a protective and decorative coating on car parts, plumbing fixtures, furniture parts and many other items, usually applied by electroplating . Chromium was used for electroplating as early as 1848, but this use only became widespread with the development of an improved process in 1924. Approximately 28.8 million metric tons (Mt) of marketable chromite ore

3901-550: The aorist. Following Homer 's practice, the augment is sometimes not made in poetry , especially epic poetry. The augment sometimes substitutes for reduplication; see below. Almost all forms of the perfect, pluperfect, and future perfect reduplicate the initial syllable of the verb stem. (A few irregular forms of perfect do not reduplicate, whereas a handful of irregular aorists reduplicate.) The three types of reduplication are: Irregular duplication can be understood diachronically. For example, lambanō (root lab ) has

3984-419: The augment when it was word-initial. In verbs with a preposition as a prefix, the augment is placed not at the start of the word, but between the preposition and the original verb. For example, προσ(-)βάλλω (I attack) goes to προσ έ βαλoν in the aorist. However compound verbs consisting of a prefix that is not a preposition retain the augment at the start of the word: αὐτο(-)μολῶ goes to ηὐ τομόλησα in

4067-446: The chromate stored in the chromate conversion coating, which is able to migrate to local defects, are the benefits of this coating method. Because of environmental and health regulations on chromates, alternative coating methods are under development. Chromic acid anodizing (or Type I anodizing) of aluminium is another electrochemical process that does not lead to the deposition of chromium, but uses chromic acid as an electrolyte in

4150-422: The chrome oxide green is chromium(III) oxide . Ancient Greek Ancient Greek ( Ἑλληνῐκή , Hellēnikḗ ; [hellɛːnikɛ́ː] ) includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek ( c.  1400–1200 BC ), Dark Ages ( c.  1200–800 BC ),

4233-458: The chromium atoms to temporarily ionize and bond with themselves, are present because the body-centric cubic's magnetic properties are disproportionate to the lattice periodicity . This is due to the magnetic moments at the cube's corners and the unequal, but antiparallel, cube centers. From here, the frequency-dependent relative permittivity of chromium, deriving from Maxwell's equations and chromium's antiferromagnetism , leaves chromium with

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4316-445: The deep shade of red pigment chrome red , which is simply lead chromate with lead(II) hydroxide (PbCrO 4 ·Pb(OH) 2 ). A very important chromate pigment, which was used widely in metal primer formulations, was zinc chromate, now replaced by zinc phosphate. A wash primer was formulated to replace the dangerous practice of pre-treating aluminium aircraft bodies with a phosphoric acid solution. This used zinc tetroxychromate dispersed in

4399-615: The dialect of Sparta ), and Northern Peloponnesus Doric (including Corinthian ). All the groups were represented by colonies beyond Greece proper as well, and these colonies generally developed local characteristics, often under the influence of settlers or neighbors speaking different Greek dialects. After the conquests of Alexander the Great in the late 4th century BC, a new international dialect known as Koine or Common Greek developed, largely based on Attic Greek , but with influence from other dialects. This dialect slowly replaced most of

4482-530: The dialects is: West vs. non-West Greek is the strongest-marked and earliest division, with non-West in subsets of Ionic-Attic (or Attic-Ionic) and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Often non-West is called 'East Greek'. Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian Greek had come under

4565-567: The divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period. They have the same general outline but differ in some of the detail. The only attested dialect from this period is Mycenaean Greek , but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups already existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not later than 1120 BC, at

4648-419: The energy-consuming change in oxidation state, the use of chromium(III) sulfate is under development; for most applications of chromium, the previously established process is used. In the chromate conversion coating process, the strong oxidative properties of chromates are used to deposit a protective oxide layer on metals like aluminium, zinc, and cadmium. This passivation and the self-healing properties of

4731-546: The formation of chromium(III) oxide. It has a strong color, and was used for school buses in the United States and for the postal services (for example, the Deutsche Post ) in Europe. The use of chrome yellow has since declined due to environmental and safety concerns and was replaced by organic pigments or other alternatives that are free from lead and chromium. Other pigments that are based around chromium are, for example,

4814-515: The formation of discrete, stable, metal, carbide particles at the grain boundaries. For example, Inconel 718 contains 18.6% chromium. Because of the excellent high-temperature properties of these nickel superalloys , they are used in jet engines and gas turbines in lieu of common structural materials. ASTM B163 relies on chromium for condenser and heat-exchanger tubes, while castings with high strength at elevated temperatures that contain chromium are standardised with ASTM A567. AISI type 332

4897-496: The insoluble iron oxide. The chromate is converted by sulfuric acid into the dichromate. The dichromate is converted to the chromium(III) oxide by reduction with carbon and then reduced in an aluminothermic reaction to chromium. The creation of metal alloys account for 85% of the available chromium's usage. The remainder of chromium is used in the chemical , refractory , and foundry industries. The strengthening effect of forming stable metal carbides at grain boundaries, and

4980-530: The majority of transition metals. However, it still has the second highest melting point out of all the period 4 elements , being topped by vanadium by 3 °C (5 °F) at 1910 °C (3470 °F). The boiling point of 2671 °C (4840 °F), however, is comparatively lower, having the fourth lowest boiling point out of the Period 4 transition metals alone behind copper , manganese and zinc . The electrical resistivity of chromium at 20 °C

5063-428: The metal. Chromium metal treated in this way readily dissolves in weak acids. The surface chromia Cr 2 O 3 scale, is adherent to the metal. In contrast, iron forms a more porous oxide which is weak and flakes easily and exposes fresh metal to the air, causing continued rusting . At room temperature, the chromia scale is a few atomic layers thick, growing in thickness by outward diffusion of metal ions across

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5146-518: The national championship for junior players born in 1999-2000 on home ice [8] [9] [10] and in 2017 there was a victory in Oral . [11] Chromium Chromium is a chemical element ; it has symbol Cr and atomic number 24. It is the first element in group 6 . It is a steely-grey, lustrous , hard, and brittle transition metal . Chromium is valued for its high corrosion resistance and hardness . A major development in steel production

5229-426: The native metal. This mine is a kimberlite pipe, rich in diamonds , and the reducing environment helped produce both elemental chromium and diamonds. The relation between Cr(III) and Cr(VI) strongly depends on pH and oxidative properties of the location. In most cases, Cr(III) is the dominating species, but in some areas, the ground water can contain up to 39 μg/L of total chromium, of which 30 μg/L

5312-508: The older dialects, although the Doric dialect has survived in the Tsakonian language , which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek . By about the 6th century AD, the Koine had slowly metamorphosed into Medieval Greek . Phrygian is an extinct Indo-European language of West and Central Anatolia , which

5395-643: The oxidative roasting of chromite ore with sodium carbonate . The change in equilibrium is visible by a change from yellow (chromate) to orange (dichromate), such as when an acid is added to a neutral solution of potassium chromate . At yet lower pH values, further condensation to more complex oxyanions of chromium is possible. Both the chromate and dichromate anions are strong oxidizing reagents at low pH: They are, however, only moderately oxidizing at high pH: Chromium(VI) compounds in solution can be detected by adding an acidic hydrogen peroxide solution. The unstable dark blue chromium(VI) peroxide (CrO 5 )

5478-446: The oxide in a charcoal oven, for which he is credited as the one who truly discovered the element. Vauquelin was also able to detect traces of chromium in precious gemstones , such as ruby and emerald . During the nineteenth century, chromium was primarily used not only as a component of paints, but in tanning salts as well. For quite some time, the crocoite found in Russia was the main source for such tanning materials. In 1827,

5561-456: The pale green [CrCl(H 2 O) 5 ]Cl 2 and violet [Cr(H 2 O) 6 ]Cl 3 . If anhydrous violet chromium(III) chloride is dissolved in water, the violet solution turns green after some time as the chloride in the inner coordination sphere is replaced by water. This kind of reaction is also observed with solutions of chrome alum and other water-soluble chromium(III) salts. A tetrahedral coordination of chromium(III) has been reported for

5644-487: The perfect stem eilēpha (not * lelēpha ) because it was originally slambanō , with perfect seslēpha , becoming eilēpha through compensatory lengthening. Reduplication is also visible in the present tense stems of certain verbs. These stems add a syllable consisting of the root's initial consonant followed by i . A nasal stop appears after the reduplication in some verbs. The earliest extant examples of ancient Greek writing ( c.  1450 BC ) are in

5727-415: The principal ions at this oxidation state. They exist at an equilibrium, determined by pH: Chromium(VI) oxyhalides are known also and include chromyl fluoride (CrO 2 F 2 ) and chromyl chloride ( CrO 2 Cl 2 ). However, despite several erroneous claims, chromium hexafluoride (as well as all higher hexahalides) remains unknown, as of 2020. Sodium chromate is produced industrially by

5810-423: The production of pure chromium, the iron must be separated from the chromium in a two step roasting and leaching process. The chromite ore is heated with a mixture of calcium carbonate and sodium carbonate in the presence of air. The chromium is oxidized to the hexavalent form, while the iron forms the stable Fe 2 O 3 . The subsequent leaching at higher elevated temperatures dissolves the chromates and leaves

5893-429: The reduction of chromium(VI) by cytochrome c7 . The Cr ion has a similar radius (63  pm ) to Al (radius 50 pm), and they can replace each other in some compounds, such as in chrome alum and alum . Chromium(III) tends to form octahedral complexes. Commercially available chromium(III) chloride hydrate is the dark green complex [CrCl 2 (H 2 O) 4 ]Cl. Closely related compounds are

5976-428: The rest of about 18% of the world production. The two main products of chromium ore refining are ferrochromium and metallic chromium. For those products the ore smelter process differs considerably. For the production of ferrochromium, the chromite ore (FeCr 2 O 4 ) is reduced in large scale in electric arc furnace or in smaller smelters with either aluminium or silicon in an aluminothermic reaction . For

6059-600: The same site as Lehmann and found a red lead mineral that was discovered to possess useful properties as a pigment in paints . After Pallas, the use of Siberian red lead as a paint pigment began to develop rapidly throughout the region. Crocoite would be the principal source of chromium in pigments until the discovery of chromite many years later. In 1794, Louis Nicolas Vauquelin received samples of crocoite ore . He produced chromium trioxide (CrO 3 ) by mixing crocoite with hydrochloric acid . In 1797, Vauquelin discovered that he could isolate metallic chromium by heating

6142-442: The scale. Above 950 °C volatile chromium trioxide CrO 3 forms from the chromia scale, limiting the scale thickness and oxidation protection. Chromium, unlike iron and nickel, does not suffer from hydrogen embrittlement . However, it does suffer from nitrogen embrittlement , reacting with nitrogen from air and forming brittle nitrides at the high temperatures necessary to work the metal parts. Naturally occurring chromium

6225-414: The solution. During anodization, an oxide layer is formed on the aluminium. The use of chromic acid, instead of the normally used sulfuric acid, leads to a slight difference of these oxide layers. The high toxicity of Cr(VI) compounds, used in the established chromium electroplating process, and the strengthening of safety and environmental regulations demand a search for substitutes for chromium, or at least

6308-422: The strong increase in corrosion resistance made chromium an important alloying material for steel. High-speed tool steels contain 3–5% chromium. Stainless steel , the primary corrosion-resistant metal alloy, is formed when chromium is introduced to iron in concentrations above 11%. For stainless steel's formation, ferrochromium is added to the molten iron. Also, nickel-based alloys have increased strength due to

6391-517: The syllabic script Linear B . Beginning in the 8th century BC, however, the Greek alphabet became standard, albeit with some variation among dialects. Early texts are written in boustrophedon style, but left-to-right became standard during the classic period. Modern editions of ancient Greek texts are usually written with accents and breathing marks , interword spacing , modern punctuation , and sometimes mixed case , but these were all introduced later. The beginning of Homer 's Iliad exemplifies

6474-467: The time of the Dorian invasions —and that their first appearances as precise alphabetic writing began in the 8th century BC. The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians . The invasion is known to have displaced population to the later Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with

6557-491: The trihalides ( CrX 3 ) with the corresponding halogen at elevated temperatures. Such compounds are susceptible to disproportionation reactions and are not stable in water. Organic compounds containing Cr(IV) state such as chromium tetra t -butoxide are also known. Most chromium(I) compounds are obtained solely by oxidation of electron-rich, octahedral chromium(0) complexes. Other chromium(I) complexes contain cyclopentadienyl ligands. As verified by X-ray diffraction ,

6640-480: Was Aeolic. For example, fragments of the works of the poet Sappho from the island of Lesbos are in Aeolian. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric (including Cretan Doric ), Southern Peloponnesus Doric (including Laconian ,

6723-452: Was a pluricentric language , divided into many dialects. The main dialect groups are Attic and Ionic , Aeolic , Arcadocypriot , and Doric , many of them with several subdivisions. Some dialects are found in standardized literary forms in literature , while others are attested only in inscriptions. There are also several historical forms. Homeric Greek is a literary form of Archaic Greek (derived primarily from Ionic and Aeolic) used in

6806-452: Was produced in 2013, and converted into 7.5 Mt of ferrochromium. According to John F. Papp, writing for the USGS, "Ferrochromium is the leading end use of chromite ore, [and] stainless steel is the leading end use of ferrochromium." The largest producers of chromium ore in 2013 have been South Africa (48%), Kazakhstan (13%), Turkey (11%), and India (10%), with several other countries producing

6889-413: Was the discovery that steel could be made highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel . Stainless steel and chrome plating ( electroplating with chromium) together comprise 85% of the commercial use. Chromium is also greatly valued as a metal that is able to be highly polished while resisting tarnishing . Polished chromium reflects almost 70% of

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