Nickel

28 cobalt ← nickel → copper - ↑ Ni ↓ Pd Periodic table - Extended periodic table
General
Name, symbol, number	nickel, Ni, 28
Element category	transition metal
Group, period, block	10, 4, d
Appearance	lustrous, metallic and silvery with a gold tinge
Standard atomic weight	58.6934(2) g·mol−1
Electron configuration	[Ar] 3d8 4s2
Electrons per shell	2, 8, 16, 2
Physical properties
Phase	solid
Density (near r.t.)	8.908 g·cm−3
Liquid density at m.p.	7.81 g·cm−3
Melting point	1728 K (1455 °C, 2651 °F)
Boiling point	3186 K (2913 °C, 5275 °F)
Heat of fusion	17.48 kJ·mol−1
Heat of vaporization	377.5 kJ·mol−1
Specific heat capacity	(25 °C) 26.07 J·mol−1·K−1
Vapor pressure P/Pa 1 10 100 1 k 10 k 100 k at T/K 1783 1950 2154 2410 2741 3184
Atomic properties
Crystal structure	face centered cubic 0.3520 nm
Oxidation states	4 [1], 3, 2, 1 [2] (mildly basic oxide)
Electronegativity	1.91 (Pauling scale)
Ionization energies (more)	1st: 737.1 kJ·mol−1
	2nd: 1753.0 kJ·mol−1
	3rd: 3395 kJ·mol−1
Atomic radius	135 pm
Atomic radius (calc.)	149 pm
Covalent radius	121 pm
Van der Waals radius	163 pm
Miscellaneous
Magnetic ordering	ferromagnetic
Electrical resistivity	(20 °C) 69.3 nΩ·m
Thermal conductivity	(300 K) 90.9 W·m−1·K−1
Thermal expansion	(25 °C) 13.4 µm·m−1·K−1
Speed of sound (thin rod)	(r.t.) 4900 m·s−1
Young's modulus	200 GPa
Shear modulus	76 GPa
Bulk modulus	180 GPa
Poisson ratio	0.31
Mohs hardness	4.0
Vickers hardness	638 MPa
Brinell hardness	700 MPa
CAS registry number	7440-02-0
Selected isotopes
Main article: Isotopes of nickel iso NA half-life DM DE (MeV) DP 56Ni syn 6.075 d ε - 56Co γ 0.158, 0.811 - 58Ni 68.077% 58Ni is stable with 30 neutrons 59Ni syn 76000 y ε - 59Co 60Ni 26.233% 60Ni is stable with 32 neutrons 61Ni 1.14% 61Ni is stable with 33 neutrons 62Ni 3.634% 62Ni is stable with 34 neutrons 63Ni syn 100.1 y β- 0.0669 63Cu 64Ni 0.926% 64Ni is stable with 36 neutrons
References

Nickel (pronounced /ˈnɪkəl/) is a metallic chemical element with the symbol Ni and atomic number 28. It is corrosion-resistant, finding many uses as in alloys and as a plating.

Characteristics

Nickel

Nickel is a silvery-white metal that takes a high polish. It belongs to the transition metals and is hard and ductile. It occurs most usually in combination with sulfur and iron in pentlandite, with sulfur in millerite, with arsenic in the mineral nickeline, and with arsenic and sulfur in nickel glance.^[1][2][3]

Similar to the massive forms of chromium, aluminium and titanium, nickel is a very reactive element, but is slow to react in air at normal temperatures and pressures. Due to its permanence in air and its inertness to oxidation, it is used in coins, for plating iron, brass, etc., for chemical apparatus, and in certain alloys, such as German silver.

Nickel is magnetic, and is very often accompanied by cobalt, both being found in meteoric iron. It 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.^[4] In the case of Nickel, this change in length is negative (contraction of the material), which is known as negative magnetostriction.

The most common oxidation state of nickel is +2, Ni complexes are observed. It is also thought that a +6 oxidation state may exist, however, results are inconclusive.

The unit cell of nickel is a face centered cube with a lattice parameter of 0.352 nm giving a radius of the atom of 0.125 nm.^[5]

Nickel-62 is the most stable nuclide of all the existing elements; it is more stable even than iron-56.

History

The use of nickel is ancient, and can be traced back as far as 3500 BC. Bronzes from what is now Syria had a nickel content of up to 2%. Further, there are Chinese manuscripts suggesting that "white copper" (i.e. baitung) was used there between 1700 and 1400 BC. However, because the ores of nickel were easily mistaken for ores of silver, any understanding of this metal and its use dates to more contemporary times. Nickel is used today as common household utensils, such as silverware.

The white copper (Paktong) was exported to Britain as early as the 17th century, but it took up to 1822 when it was discovered it contains nickel.^[6]

Minerals containing nickel (e.g. German: Kupfernickel, Old or Low German: Kopper-Nickel or Koppernickel, meaning false copper) were of value for colouring glass green. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel (now called niccolite), and obtained instead a white metal that he called nickel.^[7]

Nickel is a mischievous sprite in German mythology. It became the name of the metal through a contraction of the German name for niccolite, Kupfernickel. The Kupfer element of this word is German for copper and Kupfernickel is used in the sense of "false copper" because niccolite bears a resemblance to copper-ore. The German miners were looking for copper but could obtain none from the mischievous Kupfernickel.^[8]

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. ^[9]

Occurrence

The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe, Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni, Mg)₃Si₂O₅(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: (Ni, Fe)₉S₈.

• see Ore genesis, Category:Nickel minerals

Widmanstätten pattern showing the two forms of Nickel-Iron, Kamacite and Taenite, in an octahedrite meteorite

In terms of supply, the Sudbury region of Ontario, Canada, produces about 30 percent of the world's supply of nickel. The Sudbury Basin deposit is theorized to have been created by a massive meteorite impact event early in the geologic history of Earth. Russia contains about 40% of the world's known resources at the massive Norilsk deposit in Siberia. The Russian mining company MMC Norilsk Nickel mines this for the world market, as well as the associated palladium. Other major deposits of nickel are found in France (New Caledonia), Australia, Cuba, and Indonesia. The deposits in tropical areas are typically laterites which are produced by the intense weathering of ultramafic igneous rocks and the resulting secondary concentration of nickel bearing oxide and silicate minerals. A recent development has been the exploitation of a deposit in western Turkey, especially convenient for European smelters, steelmakers and factories. The one locality in the United States where nickel was commercially mined is Riddle, Oregon, where several square miles of nickel-bearing garnierite surface deposits are located. The mine closed in 1987.^[10][11]

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 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.

Applications

Nickel superalloy jet engine (RB199) turbine blade

Nickel is used in many industrial and consumer products, including stainless steel, magnets, coinage, 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 innumerable varieties. It is also widely used for many other alloys, such as nickel brasses and bronzes, and alloys with copper, chromium, aluminium, lead, cobalt, silver, and gold.

Nickel consumption can be summarized as: nickel steels (60%), nickel-copper alloys and nickel silver (14%), malleable nickel, nickel clad, Inconel and other Superalloys (9%), plating (6%), nickel cast irons (3%), heat and electric resistance alloys, such as Nichrome (3%), nickel brasses and bronzes (2%), others (3%).^[12][13]

In the laboratory, nickel is frequently used as a catalyst for hydrogenation, most often using Raney nickel, a finely divided form of the metal.

Nickel has also been often used in coins, or occasionally as a substitute for decorative silver. The American 'nickel' five-cent coin is 75% copper. The Canadian nickel minted at various periods between 1922-81 was 99.9% nickel, and was magnetic.

Extraction and purification

Nickel output in 2005

Nickel is recovered by 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. Recent advances in hydrometallurgical processing of sulfides has led to some recent projects being built around this technology.

Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of >75% purity. Final purification of nickel oxides is performed via the Mond process, which upgrades the nickel concentrate to >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. The nickel carbonyl gas is passed into a large chamber at high temperatures in which tens of thousands of nickel spheres are maintained in constant motion. The nickel carbonyl decomposes depositing pure nickel onto the nickel spheres (known as pellets). Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 degrees Celsius to create fine powders. 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, the nickel can be taken directly in the 75% purity form, depending on the presence of any impurities.

Nickel sulfide ores undergo flotation (differential flotation if Ni/Fe ratio is too low) and then get smelted. Smelting a nickel sulfide flotation concentrate requires a MgO level of <6% otherwise the temperature at which the smelting will be run at will be too high and lead to higher operating costs. After producing the nickel matte, further processing is done via the Sherrit-Gowden process. First copper is removed by adding hydrogen sulfide, leaving a concentrate of only cobalt and nickel. Solvent extration then efficiently separates the cobalt and nickel, with the final nickel concentrate >99%.

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.

Compounds

Nickel sulfate crystals

Tetracarbonyl nickel

Nickel(II) sulfate is produced in large quantities by dissolving nickel metal or oxides in sulfuric acid. This compound is useful for electroplating nickel.

The four halides of nickel are known: nickel(II) fluoride, chloride, bromide, and iodide. Nickel(II) chloride is produced analogously by dissolving nickel residues in hydrochloric acid.

Tetracarbonylnickel (Ni(CO)₄), discovered by Ludwig Mond,^[14] is a homoleptic complex of nickel with carbon monoxide. Having no nett dipole moment, intermolecular forces are relatively weak, allowing this compound to be liquid at room temperature. Carbon monoxide reacts with nickel metal readily to give this compound; on heating, the complex decomposes back to nickel and carbon monoxide. This behavior is exploited in the Mond process for generating high-purity nickel.

Tetracoordinate nickel(II) takes both tetrahedral and square planar geometries. This is in contrast with the other group 10 elements, which exclusively exist as square planar complexes.

Nickelocene is known; it is air-sensitive. Bis(cyclooctadiene)nickel(0) is a useful intermediate in organometallic chemistry. The cod ligands are easily displaced by other ligands.

Nickel(III) oxide is used as the cathode in many rechargeable batteries, including nickel-cadmium, nickel-iron nickel hydrogen and nickel-metal hydride, and used by certain manufacturers in Li-ion batteries.

Isotopes

Main article: Isotopes of nickel

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). 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 in large quantities in type Ia supernovae and the shape of the light curve of these supernovae corresponds to the decay via beta radiation of nickel-56 to cobalt-56 and then 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 (half-life = 1.5 Myr). Because the extinct radionuclide ⁶⁰Fe had 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). ^[15] 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 "doubly magic" (like ²⁰⁸Pb) and therefore unusually stable ^[16].

The isotopes of nickel range in atomic weight from 48 u (48-Ni) to 78 u (78-Ni). 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.^[17]

Biological role

Nickel plays numerous roles in the biology of microorganisms and plants, though they were not recognized until the 1970s. 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 H₂. 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.^[18] Other nickel-containing enzymes include a class of superoxide dismutase^[19] and a glyoxalase.^[20]

Precautions

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.^[21][22] Nickel carbonyl, [Ni(CO)₄], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a 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. Nickel is an important cause of contact allergy, partly due to its use in jewelry intended for pierced ears.^[23] 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.^[24]

Metal value

As of April 5, 2007 nickel was trading at 52,300 $US/mt (52.30 $US/kg, 23.51 $US/lb or 1.47 $US/oz) ,[3] [4]. The US nickel coin contains 0.04 oz (1.25gm) of nickel, which at that price was worth 6.5 cents, along with 3.75 grams of copper worth about 3 cents, making the metal value over 9 cents. Since a nickel is worth 5 cents, this made it an attractive target for melting by people wanting to sell the metals at a profit. However, the United States Mint, in anticipation of this practice, implemented new interim rules on December 14, 2006, subject to public comment for 30 days, which criminalize the melting and export of cents and nickels.[5] Violators can be punished with a fine of up to $10,000 and/or imprisoned for a maximum of five years.

References

External links

• WebElements.com – Nickel (also used as a reference)