Antimony

01 / A closer look

Meet Antimony

Antimony has atomic number 51: every atom of this element contains 51 protons. It belongs to period 5, group 15 of the periodic table.

In a neutral atom, the number of electrons equals the number of protons. Isotopes of this element share the same atomic number but have different neutron counts.

02 / Physical properties

Melting point

903.778 K

Boiling point

1860 K

Density

6.68 g/cm³

Atomic weight

121.76 ± 0.01

Melting points, boiling points and densities follow RSC fact boxes. Density is referenced to room temperature; consult the source for pressure and allotrope details. These are reference values, not a claim that every value was experimentally measured. Atomic weights follow CIAAW.

Physical-property source: Royal Society of Chemistry ↗ · Reviewed 24 September 2026

Standard atomic weights follow CIAAW 2024 (abridged). Brackets show an isotope mass number from IUPAC 2022, not a standard atomic weight.

03 / Atomic structure

Atomic structure

Electron configuration

[Kr]5s2 4d10 5p3

Oxidation states

+5, +3, -3

Electronegativity · Pauling

2.05

First ionisation energy

8.64 eV

Atomic radius

206 pm

04 / Where it is found

Where it is found

Stibnite is a major antimony mineral.

Production and export figures depend on the commodity and reporting year. No comparable country quantities have been included for this element in this edition.