Nickel () is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four elements that are ferromagnetic around room temperature, the other three being iron, cobalt and gadolinium.
The use of nickel has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Norilsk in Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center, which makes the metal an essential nutrient for those life forms.
Nickel is commonly found in iron meteorites as the alloys kamacite and taenite. Similar to the elements chromium, aluminium and titanium, nickel is a very reactive element, but is slow to react in air at normal temperatures and pressures due to the formation of a protective oxide surface. Due to its permanence in air and its slow rate of oxidation, it is used in coins, for plating metals such as iron and brass, for chemical apparatus, and in certain alloys such as German silver.
Nickel is chiefly valuable for the alloys it forms, especially many superalloys, and particularly stainless steel. Nickel is also a naturally magnetostrictive material, meaning that in the presence of a magnetic field, the material undergoes a small change in length. In the case of nickel, this change in length is negative (contraction of the material), which is known as negative magnetostriction and is on the order of 50 ppm. Nickel is also used as a binder in the cemented tungsten carbide or hardmetal industry and used in proportions of six to 12% by weight. Nickel can make the tungsten carbide magnetic and adds corrosion-resistant properties to the cemented tungsten carbide parts, although the hardnesses are lower than parts made of the binder cobalt.
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Characteristics
Atomic and physical properties
Nickel is a silvery-white
metal with a slight golden tinge that takes a high polish. It is one of only four elements that are magnetic at or near room temperature. Its
Curie temperature is 355 °C. That is, nickel is non-magnetic above this temperature. The unit cell of nickel is a
face centered cube with the lattice parameter of 0.352 nm giving an
atomic radius of 0.124 nm. Nickel belongs to the transition metals and is hard and
ductile.
The electronic configuration of nickel atoms contradicts
Hund's Rule. Hund's Rule, which works well for most other elements, predicts an electron shell structure of [Ar] 3d8 4s2 (the symbol [Ar] refers to the argon-like core structure). This also written as [Ar] 4s2 3d8, to emphasize that the 3d shell is the electron shell being filled by the highest-energy electrons. This configuration is incorrect, though it is found in many chemistry textbooks.
Direct investigation finds that the predominant electron structure of nickel is [Ar] 4s1 3d9, which is the more stable form because of relativistic effects.
Isotopes
Naturally occurring nickel is composed of 5 stable
isotopes;
58Ni,
60Ni,
61Ni,
62Ni and
64Ni with
58Ni being the most abundant (68.077%
natural abundance).
62Ni is one of the most stable nuclides of all the existing elements, second in stability only to
56Fe. 18
radioisotopes have been characterised with the most stable being
59Ni with a
half-life of 76,000 years,
63Ni with a half-life of 100.1 years, and
56Ni with a half-life of 6.077 days. All of the remaining
radioactive isotopes have half-lives that are less than 60 hours and the majority of these have half-lives that are less than 30 seconds. This element also has 1
meta state.
Nickel-56 is produced by the silicon burning process and later set free in large quantities during type Ia supernovae. Indeed, the shape of the light curve of these supernovae at intermediate to late-times corresponds to the decay via electron capture of nickel-56 to cobalt-56 and ultimately to iron-56. Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 76,000 years. 59Ni has found many applications in isotope geology. 59Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide 60Fe, which decays with a half-life of 2.6 million years. Because 60Fe has such a long half-life, its persistence in materials in the solar system at high enough concentrations may have generated observable variations in the isotopic composition of 60Ni. Therefore, the abundance of 60Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history. Nickel-62 has the highest binding energy per nucleon of any isotope for any element (8.7946 Mev/nucleon). Isotopes heavier than 62Ni cannot be formed by nuclear fusion without losing energy. Nickel-48, discovered in 1999, is the most proton-rich heavy element isotope known. With 28 protons and 20 neutrons 48Ni is "double magic" (like 208Pb) and therefore unusually stable.
The isotopes of nickel range in atomic weight from 48 u () to 78 u (). Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron.
Chemical properties
The most common
oxidation state of nickel is +2, but compounds of Ni
0, Ni
+, and Ni
3+ are well known, and Ni
4+ has been demonstrated.
Nickel(0)
Tetracarbonylnickel (Ni(CO)
4), discovered by
Ludwig Mond, The related nickel(0) complex
bis(cyclooctadiene)nickel(0) is a useful catalyst in
organonickel chemistry due to the easily displaced
cod ligands.
Nickel(II)
Nickel(II) compounds are known with all common anions, i.e. the sulfide, sulfate, carbonate, hydroxide, carboxylates, and halides.
Nickel(II) sulfate is produced in large quantities by dissolving nickel metal or oxides in sulfuric acid. It exists as both a hexa- and heptahydrates. This compound is useful for
electroplating nickel.
The four halogens form nickel compounds, all of which adopt octahedral geometries. Nickel(II) chloride is of particular significance, and its behavior is illustrative of the other halides. Nickel(II) chloride is produced by dissolving nickel residues in hydrochloric acid. The dichloride is usually encountered as the green hexahydrate, but it can be dehydrated to give the yellow anhydrous NiCl2. Some tetracoordinate nickel(II) complexes form both tetrahedral and square planar geometries. The tetrahedral complexes are paramagnetic and the square planar complexes are diamagnetic. This equilibrium as well as the formation of octahedral complexes contrasts with the behavior of the divalent complexes of the heavier group 10 metals, palladium(II) and platinum(II), which tend to adopt only square-planar complexes.
Nucleosynthesis
The stable form of nickel is created in
supernovas via the
r-process.
History
Because the ores of nickel are easily mistaken for ores of silver, understanding of this metal and its use dates to relatively recent times. However, the unintentional use of nickel is ancient, and can be traced back as far as 3500 BC.
Bronzes from what is now Syria had contained up to 2% nickel. Further, there are Chinese manuscripts suggesting that "white copper" (
cupronickel, known as
baitung) was used there between 1700 and 1400 BC. This Paktong white copper was exported to Britain as early as the 17th century, but the nickel content of this alloy was not discovered until 1822.
In medieval Germany, a red mineral was found in the Erzgebirge (Ore Mountains) which resembled copper ore. However, when miners were unable to extract any copper from it they blamed a mischievous sprite of German mythology, Nickel (similar to Old Nick) for besetting the copper. They called this ore Kupfernickel from the German Kupfer for copper. This ore is now known to be nickeline or niccolite, a nickel arsenide. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel and obtained instead a white metal that he named after the spirit which had given its name to the mineral, nickel. In modern German, Kupfernickel or Kupfer-Nickel designates the alloy cupronickel.
In the United States, the term "nickel" or "nick" was originally applied to the copper-nickel Indian cent coin introduced in 1859. Later, the name designated the three-cent coin introduced in 1865, and the following year the five-cent shield nickel appropriated the designation, which has remained ever since. Coins of pure nickel were first used in 1881 in Switzerland.
After its discovery the only source for nickel was the rare Kupfernickel, but from 1824 on the nickel was obtained as byproduct of cobalt blue production. The first large scale producer of nickel was Norway, which exploited nickel rich pyrrhotite from 1848 on. The introduction of nickel in steel production in 1889 increased the demand for nickel and the nickel deposits of New Caledonia, which were discovered in 1865, provided most of the world's supply between 1875 and 1915. The discovery of the large deposits in the Sudbury Basin, Canada in 1883, in Norilsk-Talnakh, Russia in 1920 and in the Merensky Reef, South Africa in 1924 made large-scale production of nickel possible. In 2005, Russia was the largest producer of nickel with about one-fifth world share closely followed by Canada, Australia and Indonesia, as reported by the British Geological Survey.
Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth's core. Kamacite and taenite are naturally occurring alloys of iron and nickel. For kamacite the alloy is usually in the proportion of 90:10 to 95:5 although impurities such as cobalt or carbon may be present, while for taenite the nickel content is between 20% and 65%. Kamacite and taenite occur in nickel-iron meteorites.
Extraction and purification
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visible, typical green, crystallized nickel-electrolyte salts in his pores.]]
Nickel is recovered through
extractive metallurgy. Most sulfide ores have traditionally been processed using
pyrometallurgical techniques to produce a
matte for further refining. Recent advances in
hydrometallurgy have resulted in recent nickel processing operations being developed using these processes. Most sulfide deposits have traditionally been processed by concentration through a
froth flotation process followed by
pyrometallurgical extraction.
Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of greater than 75% purity. Final purification of nickel oxides is performed via the Mond process, which increases the nickel concentrate to greater than 99.99% purity. This process was patented by L. Mond and was used in South Wales in the 20th century. Nickel is reacted with carbon monoxide at around 50 °C to form volatile nickel carbonyl. Any impurities remain solid while the nickel carbonyl gas passes into a large chamber at high temperatures in which tens of thousands of nickel spheres, called pellets, are constantly stirred. The nickel carbonyl decomposes, depositing pure nickel onto the nickel spheres. Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 °C to create fine nickel powder. The resultant carbon monoxide is re-circulated through the process. The highly pure nickel produced by this process is known as carbonyl nickel. A second common form of refining involves the leaching of the metal matte followed by the electro-winning of the nickel from solution by plating it onto a cathode. In many stainless steel applications, 75% pure nickel can be used without further purification depending on the composition of the impurities.
Nickel sulfide ores undergo flotation (differential flotation if Ni/Fe ratio is too low) and then are smelted. After producing the nickel matte, further processing is done via the Sherritt-Gordon process. First copper is removed by adding hydrogen sulfide, leaving a concentrate of only cobalt and nickel. Solvent extraction then efficiently separates the cobalt and nickel, with the final nickel concentration greater than 99%.
Metal value
The market price of nickel surged throughout 2006 and the early months of 2007; as of April 5, 2007, the metal was trading at 52,300 USD/
tonne or 1.47 USD/oz. The price subsequently fell dramatically from these peaks, and as of 19 January 2009 the metal was trading at 10,880 USD/tonne. Violators can be punished with a fine of up to $10,000 and/or imprisoned for a maximum of five years.
As of June 24, 2009 the melt value of a U.S. nickel is $0.0363145 which is less than the face value.
Applications
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Nickel is used in many industrial and consumer products, including
stainless steel, magnets, coinage,
rechargeable batteries, electric guitar strings and special alloys. It is also used for plating and as a green tint in glass. Nickel is pre-eminently an alloy metal, and its chief use is in the nickel steels and nickel cast irons, of which there are many varieties. It is also widely used in many other alloys, such as nickel brasses and bronzes, and alloys with copper, chromium, aluminium, lead, cobalt, silver, and gold.
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The amounts of nickel used for various applications are 60% used for making nickel steels, 14% used in nickel-copper alloys and nickel silver, 9% used to make malleable nickel, nickel clad, Inconel and other superalloys, 6% used in plating, 3% use for nickel cast irons, 3% in heat and electric resistance alloys, such as Nichrome, 2% used for nickel brasses and bronzes with the remaining 3% of the nickel consumption in all other applications combined. In the laboratory, nickel is frequently used as a catalyst for hydrogenation, sometimes Raney nickel, a finely divided form of the metal alloyed with aluminium which adsorbs hydrogen gas. Nickel is often used in coins, or occasionally as a substitute for decorative silver. The American 'nickel' five-cent coin is 75% copper and 25% nickel. The Canadian nickel minted at various periods between 1922-81 was 99.9% nickel, and was magnetic. Various other nations have historically used and still use nickel in their coinage.
Nickel is also used in fire assay as a collector of platinum group elements, as it is capable of full collection of all 6 elements, in addition to partial collection of gold. This is seen through the nature of nickel as a metal, as high throughput nickel mines may run PGE recovery (primarily platinum and palladium), such as Norilsk in Russia and the Sudbury Basin in Canada.
Nickel foam or nickel mesh is used in gas diffusion electrodes for alkaline fuel cells.
Biological role
Although not recognized until the 1970s, nickel plays important roles in the biology of microorganisms and plants. In fact
urease (an enzyme which assists in the hydrolysis of
urea) contains nickel. The NiFe-
hydrogenases contain nickel in addition to
iron-sulfur clusters. Such [NiFe]-hydrogenases characteristically oxidise H
2. A nickel-tetrapyrrole coenzyme,
F430, is present in the methyl
coenzyme M reductase which powers
methanogenic
archaea. One of the carbon monoxide dehydrogenase enzymes consists of an Fe-Ni-S cluster. Other nickel-containing enzymes include a class of
superoxide dismutase and a
glyoxalase.
Toxicity
Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be
carcinogenic, and various other nickel compounds may be as well.
Nickel carbonyl, [Ni(CO)
4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of the metal as well as the carbonyl's ability to give off highly toxic
carbon monoxide gas, and this one is no exception. It is explosive in air.
Sensitized individuals may show an
allergy to nickel affecting their skin, also known as
dermatitis. Sensitivity to nickel may also be present in patients with
pompholyx. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for
pierced ears. Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the
European Union. In 2002 researchers found amounts of nickel being emitted by 1 and 2
Euro coins far in excess of those standards. This is believed to be due to a
galvanic reaction.
It was voted Allergen of the Year in 2008 by the American Contact Dermatitis Society.
See also
:Category:Nickel alloys
Nickel aluminide
Raney nickel
Superalloy
References
External links
WebElements.com – Nickel
Category:Chemical elements
Category:Dietary minerals
Category:Ferromagnetic materials
Category:German loanwords
Category:Transition metals
Category:IARC Group 2B carcinogens
Category:Biology and pharmacology of chemical elements
