Nickel (Ni)

Nickel is one of only four elements that are ferromagnetic at room temperature, alongside iron, cobalt and gadolinium. Roughly two-thirds of world production goes into stainless steel, where it is what makes the austenitic grades non-magnetic and easy to form — the test of holding a magnet to a sink is really a test for nickel. It is also the commonest cause of allergic contact dermatitis in the developed world, affecting on the order of 10% of women, which is why the EU regulates how much nickel jewellery may release.

Properties

Atomic number

28

Symbol

Ni

Standard atomic weight

58.693 u

Category

Transition metal

Group

10

Period

4

Block

d-block

Electron configuration

[Ar] 4s² 3d⁸

Electrons per shell

2, 8, 16, 2

Melting point

1,728 K — 1454.8 °C — 2650.7 °F

Boiling point

3,186 K — 2912.8 °C — 5275.1 °F

Density

8.912 g/cm³

Electronegativity

1.91 (Pauling)

Oxidation states

+2, +3

Discovered

1751 by Axel Fredrik Cronstedt

Electron configuration

Full

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁸

Noble gas shorthand

[Ar] 4s² 3d⁸

Shells

K: 2 · L: 8 · M: 16 · N: 2

What it is used for

• Stainless steel — the 8% in "18/8" cutlery
• Nickel-metal hydride and lithium-ion battery cathodes
• Superalloys for jet engine turbine blades
• Electroplating, both decorative and for wear resistance
• Coinage, including the US five-cent piece that took its name

Hazards

• A common skin sensitiser; nickel allergy is usually lifelong once acquired
• Nickel refinery dust and nickel subsulfide are classified as carcinogenic by inhalation
• Nickel carbonyl, formed in some refining routes, is extraordinarily toxic

Neighbours in the table

Group 10

Elements in the same group share their outer electron count, which is why they behave similarly in reactions. Nickel sits in group 10 with palladium, platinum, darmstadtium.