Zinc is a chemical element with symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. In some respects zinc is chemically similar to magnesium: both elements exhibit only one normal oxidation state, the Zn2+ and Mg2+ ions are of similar size. Zinc has five stable isotopes; the most common zinc ore is sphalerite, a zinc sulfide mineral. The largest workable lodes are in Australia and the United States. Zinc is refined by froth flotation of the ore and final extraction using electricity. Brass, an alloy of copper and zinc in various proportions, was used as early as the third millennium BC in the Aegean, the United Arab Emirates, Kalmykia and Georgia, the second millennium BC in West India, Iran, Syria and Israel/Palestine. Zinc metal was not produced on a large scale until the 12th century in India, though it was known to the ancient Romans and Greeks; the mines of Rajasthan have given definite evidence of zinc production going back to the 6th century BC. To date, the oldest evidence of pure zinc comes from Zawar, in Rajasthan, as early as the 9th century AD when a distillation process was employed to make pure zinc.
Alchemists burned zinc in air to form what they called "philosopher's wool" or "white snow". The element was named by the alchemist Paracelsus after the German word Zinke. German chemist Andreas Sigismund Marggraf is credited with discovering pure metallic zinc in 1746. Work by Luigi Galvani and Alessandro Volta uncovered the electrochemical properties of zinc by 1800. Corrosion-resistant zinc plating of iron is the major application for zinc. Other applications are in electrical batteries, small non-structural castings, alloys such as brass. A variety of zinc compounds are used, such as zinc carbonate and zinc gluconate, zinc chloride, zinc pyrithione, zinc sulfide, dimethylzinc or diethylzinc in the organic laboratory. Zinc is an essential mineral, including to postnatal development. Zinc deficiency affects about two billion people in the developing world and is associated with many diseases. In children, deficiency causes growth retardation, delayed sexual maturation, infection susceptibility, diarrhea.
Enzymes with a zinc atom in the reactive center are widespread in biochemistry, such as alcohol dehydrogenase in humans. Consumption of excess zinc may cause ataxia and copper deficiency. Zinc is a bluish-white, diamagnetic metal, though most common commercial grades of the metal have a dull finish, it is somewhat less dense than iron and has a hexagonal crystal structure, with a distorted form of hexagonal close packing, in which each atom has six nearest neighbors in its own plane and six others at a greater distance of 290.6 pm. The metal is hard and brittle at most temperatures but becomes malleable between 100 and 150 °C. Above 210 °C, the metal can be pulverized by beating. Zinc is a fair conductor of electricity. For a metal, zinc has low melting and boiling points; the melting point is the lowest of all the d-block metals aside from cadmium. Many alloys contain zinc, including brass. Other metals long known to form binary alloys with zinc are aluminium, bismuth, iron, mercury, tin, cobalt, nickel and sodium.
Although neither zinc nor zirconium are ferromagnetic, their alloy ZrZn2 exhibits ferromagnetism below 35 K. A bar of zinc generates a characteristic sound when bent, similar to tin cry. Zinc makes up about 75 ppm of Earth's crust. Soil contains zinc in 5–770 ppm with an average 64 ppm. Seawater has only 30 ppb and the atmosphere, 0.1–4 µg/m3. The element is found in association with other base metals such as copper and lead in ores. Zinc is a chalcophile, meaning the element is more to be found in minerals together with sulfur and other heavy chalcogens, rather than with the light chalcogen oxygen or with non-chalcogen electronegative elements such as the halogens. Sulfides formed as the crust solidified under the reducing conditions of the early Earth's atmosphere. Sphalerite, a form of zinc sulfide, is the most mined zinc-containing ore because its concentrate contains 60–62% zinc. Other source minerals for zinc include smithsonite, hemimorphite and sometimes hydrozincite. With the exception of wurtzite, all these other minerals were formed by weathering of the primordial zinc sulfides.
Identified world zinc resources total about 1.9–2.8 billion tonnes. Large deposits are in Australia and the United States, with the largest reserves in Iran; the most recent estimate of reserve base for zinc was made in 2009 and calculated to be 480 Mt. Zinc reserves, on the other hand, are geologically identified ore bodies whose suitability for recovery is economically based at the time of determination. Since exploration and mine development is an ongoing process, the amount of zinc reserves is not a fixed number and sustainability of zinc ore supplies cannot be judged by extrapolating the combined mine life of today's zinc mines; this concept is well supported by data from the United States Geol
Austria the Republic of Austria, is a country in Central Europe comprising 9 federated states. Its capital, largest city and one of nine states is Vienna. Austria has an area of 83,879 km2, a population of nearly 9 million people and a nominal GDP of $477 billion, it is bordered by the Czech Republic and Germany to the north and Slovakia to the east and Italy to the south, Switzerland and Liechtenstein to the west. The terrain is mountainous, lying within the Alps; the majority of the population speaks local Bavarian dialects as their native language, German in its standard form is the country's official language. Other regional languages are Hungarian, Burgenland Croatian, Slovene. Austria played a central role in European History from the late 18th to the early 20th century, it emerged as a margraviate around 976 and developed into a duchy and archduchy. In the 16th century, Austria started serving as the heart of the Habsburg Monarchy and the junior branch of the House of Habsburg – one of the most influential royal houses in history.
As archduchy, it was a major component and administrative centre of the Holy Roman Empire. Following the Holy Roman Empire's dissolution, Austria founded its own empire in the 19th century, which became a great power and the leading force of the German Confederation. Subsequent to the Austro-Prussian War and the establishment of a union with Hungary, the Austro-Hungarian Empire was created. Austria was involved in both world wars. Austria is a parliamentary representative democracy with a President as head of state and a Chancellor as head of government. Major urban areas of Austria include Graz, Linz and Innsbruck. Austria is ranked as one of the richest countries in the world by per capita GDP terms; the country has developed a high standard of living and in 2018 was ranked 20th in the world for its Human Development Index. The republic declared its perpetual neutrality in foreign political affairs in 1955. Austria has been a member of the United Nations since 1955 and joined the European Union in 1995.
It is a founding member of the OECD and Interpol. Austria signed the Schengen Agreement in 1995, adopted the euro currency in 1999; the German name for Austria, Österreich, derives from the Old High German Ostarrîchi, which meant "eastern realm" and which first appeared in the "Ostarrîchi document" of 996. This word is a translation of Medieval Latin Marchia orientalis into a local dialect. Another theory says that this name comes from the local name of the mountain whose original Slovenian name is "Ostravica" - because it is steep on both sides. Austria was a prefecture of Bavaria created in 976; the word "Austria" was first recorded in the 12th century. At the time, the Danube basin of Austria was the easternmost extent of Bavaria; the Central European land, now Austria was settled in pre-Roman times by various Celtic tribes. The Celtic kingdom of Noricum was claimed by the Roman Empire and made a province. Present-day Petronell-Carnuntum in eastern Austria was an important army camp turned capital city in what became known as the Upper Pannonia province.
Carnuntum was home for 50,000 people for nearly 400 years. After the fall of the Roman Empire, the area was invaded by Bavarians and Avars. Charlemagne, King of the Franks, conquered the area in AD 788, encouraged colonization, introduced Christianity; as part of Eastern Francia, the core areas that now encompass Austria were bequeathed to the house of Babenberg. The area was known as the marchia Orientalis and was given to Leopold of Babenberg in 976; the first record showing the name Austria is from 996, where it is written as Ostarrîchi, referring to the territory of the Babenberg March. In 1156, the Privilegium Minus elevated Austria to the status of a duchy. In 1192, the Babenbergs acquired the Duchy of Styria. With the death of Frederick II in 1246, the line of the Babenbergs was extinguished; as a result, Ottokar II of Bohemia assumed control of the duchies of Austria and Carinthia. His reign came to an end with his defeat at Dürnkrut at the hands of Rudolph I of Germany in 1278. Thereafter, until World War I, Austria's history was that of its ruling dynasty, the Habsburgs.
In the 14th and 15th centuries, the Habsburgs began to accumulate other provinces in the vicinity of the Duchy of Austria. In 1438, Duke Albert V of Austria was chosen as the successor to his father-in-law, Emperor Sigismund. Although Albert himself only reigned for a year, henceforth every emperor of the Holy Roman Empire was a Habsburg, with only one exception; the Habsburgs began to accumulate territory far from the hereditary lands. In 1477, Archduke Maximilian, only son of Emperor Frederick III, married the heiress Maria of Burgundy, thus acquiring most of the Netherlands for the family. In 1496, his son Philip the Fair married Joanna the Mad, the heiress of Castile and Aragon, thus acquiring Spain and its Italian and New World appendages for the Habsburgs. In 1526, following the Battle of Mohács, Bohemia and the part of Hungary not occupied by the Ottomans came under Austrian rule. Ottoman expansion into Hungary led to frequent conflicts between the two empires evident in the Long War of 1593 to 1606.
The Turks made incursions into Styria nearly 20 times, of which some are c
The Austrian Mint is located in Vienna and is responsible for minting Austrian coins. Since 1989 it has been a public limited company and a subsidiary of Austria's central bank Oesterreichische Nationalbank, which has its headquarters in Vienna; the Austrian Mint carries out both the design and stamping of the coins it produces. Until 2002 it was only responsible for minting the coins of the Austrian schilling; the mint produces other coins, such as gold bullion coins, as well as commemorative issues: the Vienna Philharmonic coins and the Maria Theresa thaler are produced by the Austrian mint, for example. The mint supplies circulation coins and blanks to many other countries across the world. In 1194, Duke Leopold V of Austria was paid 15 tonnes of silver by Richard the Lionheart. On his way back from the crusades Richard had been captured and imprisoned by the Duke in retaliation for a previous insult. Leopold decided to strike coins from the silver, marking the beginning of the history of minting in Vienna.
The mint was located near the Hoher Markt relocated to the Wollzeile. Subsequently, it was housed in Prince Eugene’s winter palace in Himmelpfortgasse, before moving to its present home at Heumarkt, central Vienna, in the 19th century. Though other mints were established across Austria in the past, the Vienna Principal Mint became the sole mint when the Republic of Austria was formed in 1919; the mint changed its name to Münze Österreich as it became a subsidiary of Oesterreichische Nationalbank in 1989. Austrian schilling Euro coins Euro gold and silver commemorative coins Vienna Philharmonic Oesterreichische Nationalbank Official website
The Krone or korona was the official currency of the Austro-Hungarian Empire from 1892 until the dissolution of the empire in 1918. The subunit was one hundredth of the main unit, was called a Heller in the Austrian and a fillér in the Hungarian part of the Empire; the official name of the currency was Krone in Osztrák -- magyar korona in Hungary. The Latin form Corona, abbreviated to Cor. on the smaller coins, was used for the coinage of the German-speaking part of the empire known as Cisleithania. Currency names in other ethnic languages were recognised and appeared on the banknotes: koruna in Czech, korona in Polish, корона, korona in Ukrainian, corona in Italian, krona in Slovene, kruna in Croatian, круна, kruna in Serbian, koruna in Slovak, coroană in Romanian; these terms all translate to the English word crown. The symbol of the currency was the abbreviation K. or sometimes Kr. After several earlier attempts the Austro-Hungarian Empire adopted the gold standard in 1892 according to a plan drawn up by Minister of Finance Sándor Wekerle.
This plan included the introduction of the Krone. It consisted of Fillér; the value of the Krone was set at 2 Kronen = 1 Gulden of the previous silver-based currency. From 1900 onward, Krone notes were the only legal banknotes of the Empire; the currency depreciated as a result of the First World War, financed by the issue of War Bonds rather than through taxation. Consumer prices rose sixteenfold during the war, as the government had no hesitation in running the Austro-Hungarian Bank's printing presses to pay its bills: this triggered a higher inflation rate than in other combatant countries. After the end of the First World War it was hoped that the Krone might remain the common currency of the Empire's successor states, but in January 1919 the Kingdom of Serbs and Slovenes became the first successor state to overstamp the Austro-Hungarian Bank's notes, limiting their validity to its own territory. Czechoslovakia followed suit in February 1919, on 12 March 1919 the new Republic of Austria stamped the notes circulating in its territory with "DEUTSCHÖSTERREICH".
The Austrian economy did not stabilise after the war, a period of hyperinflation followed: the money supply increased from 12 to 30 billion Kronen in 1920, to about 147 billion Kronen at the end of 1921. In August 1922 consumer prices were 14,000 times greater than before the start of the war eight years earlier; the highest-denomination banknote issued was the 500,000 Kronen note, issued in 1922. Faith in the currency had been lost, people spent money as fast as they received it. In October 1922 Austria secured a loan of 650 million gold Kronen from the League of Nations, with a League of Nations Commissioner supervising the country's finances; this stabilized the currency at a rate of 14,400 paper Kronen to 1 gold Krone. On 2 January 1923 the Austrian National Bank began operations, taking over control of the currency from the Austro-Hungarian Bank which had gone into liquidation. In December 1923 the Austrian Parliament authorised the government to issue silver 5,000, 10,000, 20,000-kronen coins which were to be designated half-Schilling and double Schilling.
The Schilling became the official currency of Austria currency on 20 December 1924, at a rate of 10,000 Kronen to 1 Schilling. In these territories of Austria-Hungary, which became part of the Kingdom of the Serbs and Slovenes in 1918, Krone banknotes were stamped by the new authorities and became issues of the Serb and Slovene krone. In 1920 this was replaced by the dinar at a rate of 1 dinar = 4 Kronen. In Czechoslovakia the currency was superseded at par; the names of the present-day koruna and haléř and the pre-Euro koruna and halier are derived from the Austro-Hungarian Krone and Heller. The Fiume Krone - was introduced on 18 April 1919 by over-printing the existing Austro-Hungarian Krone notes, under the authority of the Italian National Council of Fiume who ruled the city. There were two issues: the 1919/21 Issue, the 1920 Issue; the over-printed notes were in circulation from April 1919 to February 1921. In September 1920 the Italian Lira was introduced as the official currency; the unofficial exchange rate to the lira was 2.5 FiuK to 1 Lira.
In Hungary the Austro-Hungarian currency was overstamped and replaced by the Hungarian korona at par. The Hungarian korona was devalued by hyperinflation, due to the consequences of World War I and the Treaty of Trianon, it was replaced by the pengő on 21 January 1927, at a rate of 12,500 korona to 1 pengő. In Romania there were two issues of over-stamped notes: the 1919 First Provisional Issue, the 1919 Second Provisional Issue. Both issues included 10, 20, 50, 100, 1000, 10,000 korona denominations; the issue dates of the base Austro-Hungarian krone notes used ranged from 1902–18. Krone / korona banknotes were designed and printed in Vienna from 1900 onward; these banknotes were used throughout the Monarchy. All banknotes issued by the Austro-Hungarian Bank were bilingual in German and Hungar
The Reichsmark was the currency in Germany from 1924 until 20 June 1948 in West Germany, where it was replaced with the Deutsche Mark, until 23 June in East Germany when it was replaced by the East German mark. The Reichsmark was subdivided into 100 Reichspfennig; the Mark is an ancient Germanic weight measure, traditionally a half pound used for several coins. The Reichsmark was introduced in 1924 as a permanent replacement for the Papiermark; this was necessary due to the 1920s German inflation which had reached its peak in 1923. The exchange rate between the old Papiermark and the Reichsmark was 1 ℛℳ = 1012 Papiermark. To stabilize the economy and to smooth the transition, the Papiermark was not directly replaced by the Reichsmark, but by the Rentenmark, an interim currency backed by the Deutsche Rentenbank, owning industrial and agricultural real estate assets; the Reichsmark was put on the gold standard at the rate used by the Goldmark, with the U. S. dollar worth 4.2 ℛℳ. A number of companies were created with inadequate capital for their operations and authorized to issue bonds exchangeable at a 1:1 rate for Reichsmarks and sold at a discount.
The Reichsbank rediscounted the bills of these companies creating a monetary expansion without formally renouncing the link to gold. Deutsche Gesellschaft für öffentliche Arbeiten AG, founded 1 August 1930, ended up issuing 1.26 billion Reichsmarks of Öffa bills to finance public construction. It formed the baseline model for further fraudulent issues of bills. MEFO was a dummy company, formed with small amounts of capital, used to finance German rearmament off the books, it issued bills without backing by its own resources but which were guaranteed redeemable at 1:1 for Reichsmarks for five years by the government. The MEFO bills amounts were considered a state secret and were an important element in the impression that Hitlerian economics was a success; this company created a large amount of Reichsmarks off the books, inflating the currency in secret. Payment was about to come due giving Hitler the option of shifting the German economy to export goods to pay the bills or going to war and paying the debts off from looting profits extracted from conquered states.
With the unification of Germany and Austria in 1938, the Reichsmark replaced the Schilling in Austria. During the Second World War, Germany established fixed exchange rates between the Reichsmark and the currencies of the occupied and allied countries set so as to give the Germans economic benefits; the rates were as follows: After the Second World War, the Reichsmark continued to circulate in Germany, but with new banknotes printed in the US and in the Soviet Zone, as well as with coins. In practice, massive inflation dating back to the latter stages of the war had rendered the Reichsmark nearly worthless. For all intents and purposes, it was supplanted by a barter economy; the Reichsmark was replaced in June 1948 by the Deutsche Mark in the Trizone and in the same year by the East German Mark in East Germany. The 1948 currency reform under the direction of Ludwig Erhard is considered the beginning of the West German economic recovery. Three days the new currency replaced the Reichsmark in the three Western sectors of Berlin.
In November 1945, the Reichsmark was superseded by the Allied Military Schilling in Austria. In 1947 a local currency was introduced in the Saar. In 1924, coins were introduced in denominations of 1, 2, 5, 10, 50 Reichspfennig, 1 and 3 mark; the 1 and 2 Reichspfennig were struck in bronze, depicting a wheat sheaf. And the 5, 10, 50 Reichspfennig were struck in aluminium-bronze and depicted wheat stocks crossed into a stylized pattern; the two highest denominations were depicted the German eagle standard. In 1925.500 fine silver 1 and 2 Reichsmark coins were introduced for circulation, along with the first of many commemorative 3 and 5 Reichsmark coins. In 1927, nickel 50 Reichspfennig coins were introduced along with regular-type 5 Reichsmark coins, followed by the 3 Reichsmark coin in 1931. Nazi Germany had a number of mints; each mint location had its own identifiable letter. It is therefore possible to identify which mint produced what coin by noting the mint mark on the coin. Not all mints were authorized to produce coins every year.
The mints were only authorized to produce a set number of coins with some mints allocated a greater production than others. Some of the coins with particular mint marks are therefore scarcer than others. With the silver 2 and 5 Reichsmark coins, the mint mark is found under the date on the left side of the coin. On the smaller denomination Reichspfennig coins, the mint mark is found on the bottom center of the coin. A = Berlin B = Wien D = München E = Muldenhütten F = Stuttgart G = Karlsruhe J = Hamburg Four Reichspfennig coins were issued in 1932 as part of a failed attempt by the Reichskanzler Heinrich Brüning to reduce price
The euro is the official currency of 19 of the 28 member states of the European Union. This group of states is known as the eurozone or euro area, counts about 343 million citizens as of 2019; the euro is the second largest and second most traded currency in the foreign exchange market after the United States dollar. The euro is subdivided into 100 cents; the currency is used by the institutions of the European Union, by four European microstates that are not EU members, as well as unilaterally by Montenegro and Kosovo. Outside Europe, a number of special territories of EU members use the euro as their currency. Additionally, 240 million people worldwide as of 2018 use currencies pegged to the euro; the euro is the second largest reserve currency as well as the second most traded currency in the world after the United States dollar. As of August 2018, with more than €1.2 trillion in circulation, the euro has one of the highest combined values of banknotes and coins in circulation in the world, having surpassed the U.
S. dollar. The name euro was adopted on 16 December 1995 in Madrid; the euro was introduced to world financial markets as an accounting currency on 1 January 1999, replacing the former European Currency Unit at a ratio of 1:1. Physical euro coins and banknotes entered into circulation on 1 January 2002, making it the day-to-day operating currency of its original members, by March 2002 it had replaced the former currencies. While the euro dropped subsequently to US$0.83 within two years, it has traded above the U. S. dollar since the end of 2002, peaking at US$1.60 on 18 July 2008. In late 2009, the euro became immersed in the European sovereign-debt crisis, which led to the creation of the European Financial Stability Facility as well as other reforms aimed at stabilising and strengthening the currency; the euro is managed and administered by the Frankfurt-based European Central Bank and the Eurosystem. As an independent central bank, the ECB has sole authority to set monetary policy; the Eurosystem participates in the printing and distribution of notes and coins in all member states, the operation of the eurozone payment systems.
The 1992 Maastricht Treaty obliges most EU member states to adopt the euro upon meeting certain monetary and budgetary convergence criteria, although not all states have done so. The United Kingdom and Denmark negotiated exemptions, while Sweden turned down the euro in a 2003 referendum, has circumvented the obligation to adopt the euro by not meeting the monetary and budgetary requirements. All nations that have joined the EU since 1993 have pledged to adopt the euro in due course. Since 1 January 2002, the national central banks and the ECB have issued euro banknotes on a joint basis. Euro banknotes do not show. Eurosystem NCBs are required to accept euro banknotes put into circulation by other Eurosystem members and these banknotes are not repatriated; the ECB issues 8% of the total value of banknotes issued by the Eurosystem. In practice, the ECB's banknotes are put into circulation by the NCBs, thereby incurring matching liabilities vis-à-vis the ECB; these liabilities carry interest at the main refinancing rate of the ECB.
The other 92% of euro banknotes are issued by the NCBs in proportion to their respective shares of the ECB capital key, calculated using national share of European Union population and national share of EU GDP weighted. The euro is divided into 100 cents. In Community legislative acts the plural forms of euro and cent are spelled without the s, notwithstanding normal English usage. Otherwise, normal English plurals are sometimes used, with many local variations such as centime in France. All circulating coins have a common side showing the denomination or value, a map in the background. Due to the linguistic plurality in the European Union, the Latin alphabet version of euro is used and Arabic numerals. For the denominations except the 1-, 2- and 5-cent coins, the map only showed the 15 member states which were members when the euro was introduced. Beginning in 2007 or 2008 the old map is being replaced by a map of Europe showing countries outside the Union like Norway, Belarus, Russia or Turkey.
The 1-, 2- and 5-cent coins, keep their old design, showing a geographical map of Europe with the 15 member states of 2002 raised somewhat above the rest of the map. All common sides were designed by Luc Luycx; the coins have a national side showing an image chosen by the country that issued the coin. Euro coins from any member state may be used in any nation that has adopted the euro; the coins are issued in denominations of €2, €1, 50c, 20c, 10c, 5c, 2c, 1c. To avoid the use of the two smallest coins, some cash transactions are rounded to the nearest five cents in the Netherlands and Ireland and in Finland; this practice is discouraged by the Commission, as is the practice of certain shops of refusing to accept high-value euro notes. Commemorative coins with €2 face value have been issued with changes to the design of the national side of the coin; these include both issued coins, such as the €2 commemorative coin for the fiftieth anniversary of the signing of the Treaty of Rome, nationally i
Aluminium or aluminum is a chemical element with symbol Al and atomic number 13. It is a silvery-white, soft and ductile metal in the boron group. By mass, aluminium makes up about 8% of the Earth's crust; the chief ore of aluminium is bauxite. Aluminium metal is so chemically reactive that native specimens are rare and limited to extreme reducing environments. Instead, it is found combined in over 270 different minerals. Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation. Aluminium and its alloys are vital to the aerospace industry and important in transportation and building industries, such as building facades and window frames; the oxides and sulfates are the most useful compounds of aluminium. Despite its prevalence in the environment, no known form of life uses aluminium salts metabolically, but aluminium is well tolerated by plants and animals; because of these salts' abundance, the potential for a biological role for them is of continuing interest, studies continue.
Of aluminium isotopes, only 27Al is stable. This is consistent with aluminium having an odd atomic number, it is the only aluminium isotope that has existed on Earth in its current form since the creation of the planet. Nearly all the element on Earth is present as this isotope, which makes aluminium a mononuclidic element and means that its standard atomic weight equates to that of the isotope; the standard atomic weight of aluminium is low in comparison with many other metals, which has consequences for the element's properties. All other isotopes of aluminium are radioactive; the most stable of these is 26Al and therefore could not have survived since the formation of the planet. However, 26Al is produced from argon in the atmosphere by spallation caused by cosmic ray protons; the ratio of 26Al to 10Be has been used for radiodating of geological processes over 105 to 106 year time scales, in particular transport, sediment storage, burial times, erosion. Most meteorite scientists believe that the energy released by the decay of 26Al was responsible for the melting and differentiation of some asteroids after their formation 4.55 billion years ago.
The remaining isotopes of aluminium, with mass numbers ranging from 21 to 43, all have half-lives well under an hour. Three metastable states are known, all with half-lives under a minute. An aluminium atom has 13 electrons, arranged in an electron configuration of 3s23p1, with three electrons beyond a stable noble gas configuration. Accordingly, the combined first three ionization energies of aluminium are far lower than the fourth ionization energy alone. Aluminium can easily surrender its three outermost electrons in many chemical reactions; the electronegativity of aluminium is 1.61. A free aluminium atom has a radius of 143 pm. With the three outermost electrons removed, the radius shrinks to 39 pm for a 4-coordinated atom or 53.5 pm for a 6-coordinated atom. At standard temperature and pressure, aluminium atoms form a face-centered cubic crystal system bound by metallic bonding provided by atoms' outermost electrons; this crystal system is shared by some other metals, such as copper. Aluminium metal, when in quantity, is shiny and resembles silver because it preferentially absorbs far ultraviolet radiation while reflecting all visible light so it does not impart any color to reflected light, unlike the reflectance spectra of copper and gold.
Another important characteristic of aluminium is its low density, 2.70 g/cm3. Aluminium is a soft, lightweight and malleable with appearance ranging from silvery to dull gray, depending on the surface roughness, it is nonmagnetic and does not ignite. A fresh film of aluminium serves as a good reflector of visible light and an excellent reflector of medium and far infrared radiation; the yield strength of pure aluminium is 7–11 MPa, while aluminium alloys have yield strengths ranging from 200 MPa to 600 MPa. Aluminium has stiffness of steel, it is machined, cast and extruded. Aluminium atoms are arranged in a face-centered cubic structure. Aluminium has a stacking-fault energy of 200 mJ/m2. Aluminium is a good thermal and electrical conductor, having 59% the conductivity of copper, both thermal and electrical, while having only 30% of copper's density. Aluminium is capable of superconductivity, with a superconducting critical temperature of 1.2 kelvin and a critical magnetic field of about 100 gauss.
Aluminium is the most common material for the fabrication of superconducting qubits. Aluminium's corrosion resistance can be excellent due to a thin surface layer of aluminium oxide that forms when the bare metal is exposed to air preventing further oxidation, in a process termed passivation; the strongest aluminium alloys are less corrosion resistant due to galvanic reactions with alloyed copper. This corrosion resistance is reduced by aqueous salts in the presence of dissimilar metals. In acidic solutions, aluminium reacts with water to form hydrogen, in alkaline ones to form aluminates—protective passivation under these conditions is negligible; because it is corroded by dissolved chlorides, such as common sodium chloride, household plumbing is never made from aluminium. However, because