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Nickel,  28Ni
Nickel powder.jpg
Nickel metal in powdered form
General properties
Name, symbol Nickel, Ni
Appearance A silvery metal that resists corrosion even at high temperatures.
Nickel in the periodic table


Atomic number 28
Standard atomic weight (Ar) 58.6934(4)
Group, block , d-block
Period period 4
Electron configuration

[Ar] 3d8 4s2 or

[Ar] 3d9 4s1
per shell
2, 8, 16, 2 or 2, 8, 17, 1
Physical properties
Silvery metallic
Phase Solid
Melting point 1728 K ​(1455 °C, ​2651 °F)
Boiling point 3003 K ​(2730 °C, ​4946 °F)
Density near r.t. 8.908 g/cm3
when liquid, at  7.81 g/cm3
Heat of fusion 17.48 kJ/mol
Heat of 379 kJ/mol
Molar heat capacity 26.07 J/(mol·K)
Atomic properties
Oxidation states 4, 3, 2, 1, -1, -2 ​(a mildly basic oxide)
Electronegativity Pauling scale: 1.91
energies 1st: 737.129 kJ/mol
2nd: 1753.027 kJ/mol
3rd: 3395.32 kJ/mol
Atomic radius empirical: 124 pm
Covalent radius 124±4 pm
Van der Waals radius 163 pm
Crystal structure ​Face-centered cubic (fcc)
Speed of sound thin rod 4900 m/s (at )
Thermal expansion 13.4 µm/(m·K) (at 25 °C)
Thermal conductivity 90.9 W/(m·K)
Electrical resistivity 6.93·10-8 Ω·m (at 20 °C)
Magnetic ordering Ferromagnetic
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 667–1600 MPa
CAS Registry Number 7440-02-0
Discovery and first isolation Axel Fredrik Cronstedt (1751)
· references

Nickel is a transition metal with the symbol Ni and atomic number 28. It is well-known as a coinage material due to its corrosion resistance, and is often used to plate objects. In solution, it has extensive coordination chemistry, and some interesting redox chemistry which is not commonly seen.


Physical properties

Nickel is a silvery-white metal that has a slight yellowish tinge. It is one of four elements that is ferromagnetic at or near room temperature (iron, cobalt, and gadolinium being the others). Its Curie temperature is 355 °C, which causes the metal to reversibly become paramagnetic. It is hard yet ductile.

Chemical properties

Much of nickel's chemical resistance owes to its passivation in air. It will also passivate in the presence of fluorine, making it an ideal material for handling and storing the gas. It will dissolve only slowly in hydrochloric and sulfuric acids. In concentrated nitric acid, nickel will not dissolve, but it will dissolve in dilute nitric acid.

Nickel(II) compounds form a hexaaqua complex in water with the formula [Ni(H2O)6]2+ and coordinate to many different ligands, including chloride, ammonia, and ethylenediamine. These complexes can be hexacoordinate, tetragonal, or square planar, with square planar complexes such as tetrachloronickelate being diamagnetic rather than paramagnetic.


Nickel is present as the main material (certified 99.9%) in older Canadian nickels, dating from 1922 to 1942, and older Canadian dimes dating from 1969 to 1999. It is also present in US nickels, dimes, quarters and in 1 and 2 euro coins too. However, the majority of the metal is copper, with nickel making up anywhere from 9% to 25% of the coin. Destroying coins is illegal however, and heavy fines exist everywhere for breaking this law.

A good source of nickel is Mu-metal, an alloy containing 77-80% nickel, 16% iron, 5-2% copper and molybdenum. This alloy is commonly encountered in the hard drive magnets brackets, which can be extracted from hard disks. As a bonus, they are also nickel plated. Old submarine cables also contain Mu-metal wiring. Cathode tubes are also a source. Chemical extraction is required to separate the nickel.

Nickel strips for electroplating can be bought from United Nuclear.

Another good source of nickel metal is the Ni200 wire sold in many electronic cigarette stores, as heating wire. The nickel content is 99%.




Nickel compounds are known to be carcinogens, and are grouped as class 1. Nickel metal is grouped as class 2B (it is a suspected carcinogen). However, it is not regulated by OSHA.

Some people are allergic to nickel metal and develop an itch or rash when exposed to it (contact dermatitis). If this occurs, wear gloves when handling the metal.


No special storage is required for bulk nickel. Nickel powder must be stored in closed bottles, away from any ignition source.


Nickel and its compounds should be taken to disposal facilities.


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