What Is Antimony?
Antimony is a chemical element with the symbol Sb and atomic number 51, classified as a metalloid with both metallic and nonmetallic traits.
A lustrous grey metalloid used since antiquity in cosmetics (kohl eyeliner).
As a metalloid in Period 5 and Group 15 (Nitrogen Group / Pnictogens), antimony's placement on the table reflects its electron configuration of [Kr] 4d¹⁰ 5s² 5p³, which governs its bonding behavior and the type of compounds it typically forms.
Position on the Periodic Table
Antimony is located in Period 5, which continues the transition metal pattern seen in Period 4 but one principal shell further out.
Within that row, antimony sits in Group 15 (Nitrogen Group / Pnictogens), alongside elements that share a similar number of valence electrons and, by extension, similar chemical behavior.
This position is not arbitrary — the periodic table was deliberately organized so that an element's row and column reveal its expected reactivity, bonding pattern, and physical state at a glance.
Physical & Chemical Properties
Antimony has an atomic mass of 121.760 u and a density of 6.697 g/cm³. Its melting point is 630.6°C and its boiling point is 1587°C.
As a metalloid, antimony conducts electricity better than a typical nonmetal but worse than a true metal, a property known as semiconductivity.
Electron Configuration Explained
Antimony's electron configuration is [Kr] 4d¹⁰ 5s² 5p³, describing how its electrons are distributed across shells and subshells around the nucleus.
Reading the configuration in order shows electrons filling shells of increasing energy, following the standard Aufbau principle that explains how atomic structure builds up across the periodic table.
The outermost (valence) electrons shown in this configuration are what ultimately determine antimony's chemical reactivity and the type of bonds it forms with other elements.
History & Discovery
Antimony has been known since ancient times, predating the modern, systematic study of chemical elements by thousands of years.
Its early use is traced through archaeological evidence — tools, artifacts, and written records — rather than a single documented discovery event, since ancient civilizations had no formal concept of a 'chemical element.'
What Is Antimony Used For?
Antimony's specific properties make it useful in several applications, including:
- Flame retardants
- Batteries
- Alloys
- Pigments
- Cosmetics (ancient)
These uses reflect antimony's underlying classification as a metalloid, since the same properties that define its category in chemistry also determine where it becomes practically useful.
Fun Facts About Antimony
- Ancient Egyptians used antimony sulfide as black kohl eyeliner.
- Antimony is element number 51 on the periodic table, in Period 5 and Group 15.
- Its standard atomic mass is 121.760 u, calculated from the natural abundance of its isotopes.
Frequently Asked Questions
What is Antimony's atomic number?
Antimony has atomic number 51.
What is Antimony's chemical symbol?
Antimony's symbol is Sb.
What group and period is Antimony in?
Antimony is in Period 5, Group 15 (Nitrogen Group / Pnictogens).
What is Antimony's atomic mass?
Antimony's standard atomic mass is 121.760 u.