|Name, Symbol, Number||nickel, Ni, 28|
|Chemical series||transition metals|
|Group, Period, Block||10, 4, d|
|Appearance||lustrous, metallic |
|Atomic mass||58.6934(2) g/mol|
|Electron configuration||[Ar] 3d8 4s2|
|Electrons per shell||2, 8, 16, 2|
|Density (near r.t.)||8.908 g/cm³|
|Liquid density at m.p.||7.81 g/cm³|
|Melting point||1728 K|
(1455 °C, 2651 °F)
|Boiling point||3186 K|
(2913 °C, 5275 °F)
|Heat of fusion||17.48 kJ/mol|
|Heat of vaporization||377.5 kJ/mol|
|Heat capacity||(25 °C) 26.07 J/(mol·K)|
|Crystal structure||cubic face centered|
|Oxidation states||2, 3|
(mildly basic oxide)
|Electronegativity||1.91 (Pauling scale)|
|1st: 737.1 kJ/mol|
|2nd: 1753.0 kJ/mol|
|3rd: 3395 kJ/mol|
|Atomic radius||135 pm|
|Atomic radius (calc.)||149 pm|
|Covalent radius||121 pm|
|Van der Waals radius||163 pm|
|Electrical resistivity||(20 °C) 69.3 nΩ·m|
|Thermal conductivity||(300 K) 90.9 W/(m·K)|
|Thermal expansion||(25 °C) 13.4 µm/(m·K)|
|Speed of sound (thin rod)||(r.t.) 4900 m/s|
|Speed of sound (thin rod)||(r.t.) 200 m/s|
|Shear modulus||76 GPa|
|Bulk modulus||180 GPa|
|Vickers hardness||638 MPa|
|Brinell hardness||700 MPa|
|CAS registry number||7440-02-0|
Nickel (chemical symbol Ni, atomic number 28) is a silvery white metal that takes on a high polish. In the human body, nickel is required for the function of several enzymes. In addition, 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, aluminum, lead, cobalt, silver and gold. In the laboratory, nickel is frequently used as a catalyst for hydrogenation, most often using Raney nickel, a finely divided form of the metal.
Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth's core. Scientists believe that nickel is one of the final elements (along with iron) produced by nuclear reactions that take place within stars—processes known as stellar nucleosynthesis. Iron and nickel are therefore the most abundant metals in metallic meteorites and in the dense-metal cores of planets such as Earth.
In terms of mining, the bulk of our nickel comes from two types of ore deposits:
- Laterites, where the principal ore minerals are nickeliferous limonite ((Fe,Ni)O(OH)) and garnierite ((Ni,Mg)3Si2O5(OH)).
- Magmatic sulfide deposits, where the principal ore mineral is pentlandite ((Ni,Fe)9S8).
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 has about 40 percent of the world's known resources at the massive Norilsk deposit in Siberia. Russia mines this primarily for its own domestic supply and for export of palladium. Other major deposits of nickel are found in 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 use of nickel can be traced as far back as 3500 B.C.E. Bronzes from what is now Syria had a nickel content of up to two percent. Further, there are Chinese manuscripts suggesting that "white copper" (baitung) was used in the Orient between 1400 and 1700 B.C.E. Yet, the ores of nickel were easily mistaken for ores of silver. For this reason, any understanding of this metal and its use dates to more contemporary times.
Minerals containing nickel (such as kupfernickel, meaning copper of the devil ("Nick"), or false copper) were valued for coloring 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.
In chemical terms, nickel is a member of a group of transition metals. It is located in period 4 of the periodic table, situated between cobalt and copper. In addition, it lies at the top of group 10 (former group 8B). Iron, cobalt, and nickel have a number of similar properties and were once grouped together as group 8B.
On account of its permanence in air and inertness to oxidation, it is used in the smaller coins, for plating materials such as iron and brass, for chemical apparatus, and in certain alloys, as German silver. It is magnetic, and is very frequently accompanied by cobalt, both being found in meteoric iron. It is chiefly valuable for the alloys it forms, especially many superalloys.
Nickel is one of the five ferromagnetic elements—the other four being iron, cobalt, gadolinium, and dysprosium. Thus, it can be readily magnetized and converted to a permanent magnet. However, the U.S. "nickel" coin is not magnetic because it is mostly copper, but old Canadian nickels minted until 1958 were.
The most common oxidation state of nickel is +2, though 0, +1, +3 and +4 Ni complexes are observed. It is also thought that a +6 oxidation state may exist, however, results are inconclusive.
The isotopes of nickel range in atomic weight from 48 atomic mass units (amu) (48-Ni) to 78 amu (78-Ni). Naturally occurring nickel is composed of five stable isotopes: 58-Ni, 60-Ni, 61-Ni, 62-Ni, and 64-Ni, with 58-Ni being the most abundant (68.077 percent natural abundance). Nickel-62 is the most stable nuclide of all the existing elements; it is more stable than iron-56.
Eighteen radioisotopes have been characterized, of which the three longest-lived ones are 59-Ni, with a half-life of 76,000 years; 63-Ni, with a half-life of 100.1 years; and 56-Ni, with a half-life of 6.077 days. All 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 of nickel-56 to cobalt-56 and then to iron-56.
Nickel-59 has found many applications in isotope geology. It 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 insights into the origin of the solar system and its early history.
Nickel-78 was recently found to have a half-life of 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron. 
Extraction and purification
Nickel can be recovered using extractive metallurgy. Most lateritic 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 sulphide deposits have traditionally been processed by concentration through a froth flotation process followed by pyrometallurgical extraction. Recent advances in hydrometallurgical processing of sulphides 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 greater than 75 percent purity. Final purification in the Mond process to greater than 99.99 percent purity is performed by reacting nickel and carbon monoxide to form nickel carbonyl. This gas is passed into a large chamber at a higher temperature 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 without pellets present 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 percent purity form, depending on the presence of any impurities.
The largest producer of nickel is Russia, which extracts 267,000 tons of nickel per year. Australia and Canada are the second and third largest producers, making 207 and 189.3 thousand tons per year. 1
Many but not all enzymes in the class called hydrogenases contain nickel in addition to iron-sulfur clusters. Nickel centers are a common element in those hydrogenases whose function is to oxidise rather than evolve hydrogen. The nickel center appears to undergo changes in oxidation state, and evidence has been presented that the nickel center might be the active site of these enzymes.
A nickel-tetrapyrrole coenzyme, Co-F430, is present in the methyl CoM reductase and in methanogenic bacteria. The tetrapyrrole is intermediate in structure between porphyrin and corrin. Changes in redox state, as well as changes in nickel coordination, have recently been observed.
There is also a nickel-containing carbon monoxide dehydrogenase. Little is known about the structure of the nickel site. Studies on chicks and rats (the latter of which are relatively close to humans genetically) suggest that nickel is essential for proper liver function.
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, aluminum, lead, cobalt, silver and gold.
Nickel consumption can be summarized as: nickel steels (60 percent), nickel-copper alloys and nickel silver (14 percent), malleable nickel, nickel clad and Inconel (9 percent), plating (6 percent), nickel cast irons (3 percent), heat and electric resistance alloys (3 percent), nickel brasses and bronzes (2 percent), others (3 percent).
In the laboratory, nickel is frequently used as a catalyst for hydrogenation, most often using Raney nickel, a finely divided form of the metal.
- Kamacite is a naturally occurring alloy of iron and nickel, usually in proportions ranging from 90:10 to 95:5, with possible impurities such as cobalt or carbon. Kamacite occurs in nickel-iron meteorites.
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 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.
Sensitised individuals may show an allergy to nickel affecting their skin. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 a report in the journal Nature 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.
- Note 1: Production and consumption figures are from The Economist: Pocket World in Figures 2005, Profile Books (2005). ISBN 1861977999
- Cotton, F. Albert and Wilkinson, Geoffrey. 1980. Advanced Inorganic Chemistry (4th edition). New York: Wiley & Sons. ISBN 0471027758
- Nickel — Los Alamos National Laboratory. Accessed on September 25, 2006.
- Nickel — WebElements.com. Accessed on September 25, 2006.
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