Chemical element · reference page

51Sb

Antimony

Antimony is element 51 (Sb), located in period 5, group 15 and the p block. At room temperature its reference phase is solid. Its electron configuration is [Kr] 4d10 5s2 5p3.

Atomic number51

Standard atomic weight121.760(1)

Group15

Period5

Blockp

Electron configuration[Kr] 4d10 5s2 5p3

Electronic structure

What controls its chemistry

Group 15 atoms have five valence electrons. They can form three covalent bonds, participate in multiple bonding, or adopt several oxidation states depending on the element and its bonding partners.

The configuration [Kr] 4d10 5s2 5p3 places antimony in this family, but the chemistry changes markedly from non-metallic nitrogen and phosphorus to the heavier, more metallic members.

Chemical forms

Compounds, ions and materials

Common families include hydrides, oxides, oxoacids or oxoanions, halides and compounds with metals. Oxidation states from −3 to positive values occur across the group, with the accessible range changing strongly from nitrogen to bismuth.

Physical behaviour

State and phase changes

The reference phase at room temperature is solid. The listed density is 6.697 g/cm³. The melting point is 903.8 K (630.6 °C). The boiling point is 1 908 K (1 635 °C). Pressure, purity and crystal structure can shift measured physical properties.

Occurrence and applications

Where antimony is found and used

In practice, antimony is encountered in flame retardants, alloys and semiconductors.

In practice

Examples of real uses

Flame retardants

Antimony compounds are used in selected flame-retardant formulations to alter combustion chemistry.

Alloys

Antimony is added to metals to change strength, corrosion resistance, melting behaviour or high-temperature performance.

Semiconductors

Compounds or doped forms of antimony are used to control electrical conduction in semiconductor devices.

Periodic position

What its neighbours tell us

Antimony is in period 5 and group 15. In the neighbourhood shown here, it lies between tin and tellurium in the same period; arsenic is above it and bismuth 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

Classificationmetalloid

Phase at room temperatureSolid

Electron shells2 · 8 · 18 · 18 · 5

Density6.697 g/cm³

Melting point903.8 K (630.6 °C)

Boiling point1 908 K (1 635 °C)

Pauling electronegativity2.05

First ionisation energy831kJ/mol

Electron affinity101.1 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

Antimony was known before 3000 BC, with no single discoverer identified in this record. Its early use predates modern chemistry, so use of the material, chemical identification and the later atomic-number definition are separate stages.

Isotopes and atomic weight

How isotope composition changes the numbers

The standard atomic weight is 121.760(1). This value refers to the isotopic composition of natural terrestrial material, not to the mass of one specific atom.

Antimony 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 antimony depend on chemical form, dose and route of exposure. Pure antimony, 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.