About

Antimony is a lustrous gray metalloid known for its brittleness. Its most significant use is in flame retardants, where antimony trioxide is added to plastics, textiles, and electronics to inhibit combustion and prevent them from catching fire. It is also used to harden lead alloys for lead-acid batteries and bullets, and has some applications in semiconductors.

Atomic Properties

Atomic Number51

Atomic Weight121.76 u

Neutrons (common)70

Electron Configuration[Kr] 4d¹⁰ 5s² 5p³

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p³

Electrons per Shell2, 8, 18, 18, 5

Electronegativity2.05

Electron Affinity101.06 kJ/mol

Oxidation States+5, +3, -3

Covalent Radius140 pm

Van der Waals Radius206 pm

Ionic Radius76 pm

Periodic Table Position

Group15

Period5

BlockP

Chemical SeriesMetalloids

Physical Properties

State at STPsolid

Appearancelustrous gray metalloid

Crystal Structurerhombohedral

Magnetic Orderingdiamagnetic

Speed of Sound3,420 m/s

Poisson Ratio0.31

Thermal Properties

Melting Point903.78 K

Boiling Point1,860 K

Triple Point903.78 K

Thermal Expansion0 1/K

Thermal Conductivity24.4 W/(m·K)

Specific Heat0.207 J/(g·K)

Molar Heat25.2 J/(mol·K)

Heat of Fusion19.79 kJ/mol

Heat of Vaporization77.14 kJ/mol

Abundance

In Earth's Crust0.2 ppm

In Ocean0 ppm

In Solar System0 ppm

In Human Body0.028 ppm

In Universe0 ppm

Discovery

Discovered byAncient civilizations

Discovery YearKnown since antiquity

Occurrenceprimordial

CAS Number7440-36-0

Electron Configuration

Energy

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Isotopes of Antimony

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
¹²¹Sb	120.903810	57.21%	Stable	Stable
¹²³Sb	122.904210	42.79%	Stable	Stable

Interactive Visualization

Explore the 3D Bohr model of Antimony in our interactive viewer.

View 3D Model of Antimony