Chemical element · reference page

28Ni

Nickel

Nickel is element 28 (Ni), located in period 4, group 10 and the d block. At room temperature its reference phase is solid. Its electron configuration is [Ar] 3d8 4s2.

Atomic number28

Standard atomic weight58.6934(4)

Group10

Period4

Blockd

Electron configuration[Ar] 3d8 4s2

Electronic structure

What controls its chemistry

The d subshell participates in the chemistry of nickel. Transition metals can use electrons of similar energies in bonding, which is why variable oxidation states, coordination compounds and catalytic behaviour are common across the d block.

Its electron configuration, [Ar] 3d8 4s2, should be read together with the oxidation state of the compound: removing electrons changes which d orbitals are occupied and can alter colour, magnetism, bonding and reactivity.

Chemical forms

Compounds, ions and materials

For nickel, important chemical forms include metals and alloys, oxides, halides and coordination compounds. Variable oxidation states are common because s and d electrons have similar energies, and ligands around the metal ion can strongly alter colour, magnetism and reactivity.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 8.908 g/cm³. The melting point is 1 729 K (1 456 °C). The boiling point is 3 003 K (2 730 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where nickel is found and used

In practice, nickel is encountered in stainless steel, batteries, coins and monetary alloys.

In practice

Examples of real uses

Stainless steel

Nickel is used in stainless steel alongside chromium and other alloying elements, which help stabilise the protective surface chemistry and required microstructure.

Batteries

Nickel is used in selected battery chemistries, electrode materials or electrolytes. The exact role depends on the compound and cell design.

Coins

Nickel is used in coinage alloys selected for wear resistance, corrosion behaviour, colour and ease of minting.

Monetary alloys

Nickel is used in durable coinage alloys designed to resist wear and corrosion.

Periodic position

What its neighbours tell us

Nickel is in period 4 and group 10. In the neighbourhood shown here, it lies between cobalt and copper in the same period; palladium is directly below it in the same group. These positions make it possible to compare atomic size, ionisation energy and bonding behaviour with nearby elements.

Reference data

Physical and atomic properties

Classificationtransition metal

Phase at room temperatureSolid

Electron shells2 · 8 · 16 · 2

Density8.908 g/cm³

Melting point1 729 K (1 456 °C)

Boiling point3 003 K (2 730 °C)

Pauling electronegativity1.91

First ionisation energy737.1 kJ/mol

Electron affinity111.7 kJ/mol

Values describe the element or neutral atom where applicable. Physical data can depend on allotrope, pressure and measurement conditions.

History

Discovery and identification

The discovery of nickel is associated with Axel Fredrik Cronstedt. Recognition of the element, isolation of a pure sample and assignment of its modern atomic number did not necessarily occur at the same time.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 58.6934(4). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Nickel has at least one stable isotope. Different isotopes have the same number of protons and therefore the same element identity, but different neutron numbers and atomic masses.

Safety

Handling and exposure

The hazards associated with nickel depend on chemical form, dose and route of exposure. Pure nickel, its ions and its compounds can have very different biological and environmental effects, so safety data should be checked for the actual substance being handled.