Nickel was first isolated in 1751 and is a chemical element with symbol Ni and atomic number 28. It is thought that an iron-nickel mixture composes Earth's inner core. Nickel has two electron configurations and exists as five stable isotopes, with nickel-58 being the most abundant. Nickel is used in stainless steel, magnets, batteries, and alloys and purified via the Mond process to over 99.99% purity.

2.  Nickel was first isolated and classified
as a chemical element in 1751 by Axel
Fredrik Cronstedt, who initially mistook
its orefor a copper mineral.
 Nickel is a chemical element with
symbol Ni and atomic number 28.
 An iron–nickel mixture is thought to
compose Earth's inner core.

3. PHYSICAL PROPERTIES
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·cm
−3
when liquid, at m.p. 7.81 g·cm
−3
Heat of fusion 17.48 kJ·mol
−1
Heat of vaporization 379 kJ·mol
−1
Molar heat capacity 26.07 J·mol
−1
·K
−1

4.  The nickel atom has two electron
configurations, [Ar] 3d8 4s2 and [Ar]
3d9 4s1, which are very close in energy –
the symbol [Ar] refers to the argon-like
core structure.
 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% natural abundance).

5. Miscellanea
Crystal structure face-centered cubic (fcc)
Speed of soundthin rod 4900 m·s
−1
(at r.t.)
Thermal expansion 13.4 µm·m
−1
·K
−1
(at 25 °C)
Thermal conductivity 90.9 W·m
−1
·K
−1
Electrical resistivity 69.3 nΩ·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

6.  Purification of nickel oxides to obtain the
purest metal is performed via the Mond
process, which increases the nickel
concentrate to greater than 99.99% purity.

7.  Nickel is used in many specific and
recognizable industrial and consumer
products, including stainless
steel, alnico magnets, coinage, rechargeable
batteries, electric guitar strings, microphone
capsules, and special alloys

8.  The plant enzyme urease (an enzyme that assists in the
hydrolysis of urea) contains nickel.
 Nickel can have an impact on human health through
infectious diseases arising from nickel-dependent
bacteria.[71] Nickel released from Siberian Traps volcanic
eruptions (site of the modern city of Norilsk) is suspected of
having had a significant impact on the role played
by Methanosarcina, a genus of euryarchaeote archaea that
produced methane during the biggest extinction event on
record.

9.  Nickel carbonyl, [Ni(CO)4], is an extremely
toxic gas.
 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.