Antimony
Atomic Data
| Atomic Number | 51 |
| Symbol | Sb |
| Atomic Weight | 121.76 u |
| Density (STP) | 6.697 g/cm³ |
| Melting Point | 630.63 °C (903.78 K) |
| Boiling Point | 1586.85 °C (1860 K) |
| Electronegativity | 2.05 (Pauling) |
| Electron Config. | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p3 |
| Oxidation States | −3, +3, +5 |
| Phase at STP | Solid |
| Category | Metalloid |
| Period / Group | 5 / 15 |
| CAS Number | 7440-36-0 |
Electron Configuration
[Kr] 4d10 5s2 5p3
| Shell | n | Subshell | Electrons | Cumulative |
|---|---|---|---|---|
| K | 1 | 1s | 2 | 2 |
| L | 2 | 2s | 2 | 4 |
| L | 2 | 2p | 6 | 10 |
| M | 3 | 3s | 2 | 12 |
| M | 3 | 3p | 6 | 18 |
| M | 3 | 3d | 10 | 28 |
| N | 4 | 4s | 2 | 30 |
| N | 4 | 4p | 6 | 36 |
| N | 4 | 4d | 10 | 46 |
| O | 5 | 5s | 2 | 48 |
| O | 5 | 5p | 3 | 51 |
| Total | 51 | 51 | ||
Isotopes of Antimony
Antimony has two naturally occurring stable isotopes. The most abundant is ¹²¹Sb, comprising 57.21% of all naturally occurring Antimony.
| Isotope | Symbol | Protons | Neutrons | Abundance | Stability |
|---|---|---|---|---|---|
| Antimony-121 | ¹²¹Sb | 51 | 70 | 57.21 | Stable |
| Antimony-123 | ¹²³Sb | 51 | 72 | 42.79 | Stable |
Abundance & Occurrence
Antimony is present in Earth's crust at approximately 0.2 ppm by mass and at approximately 0.4 ppm by mass throughout the universe.
Earth's Crust (ppm by mass)
Universe (ppm by mass)
Discovery & History
Read more about the discovery of the periodic table of elements →
Safety & Handling
- Stibine gas (SbH3): acute toxicity: Stibine is one of the most toxic of all antimony compounds; like arsine, it causes haemolysis and is acutely toxic even at low concentrations: handle antimony-containing alloys with acids with extreme caution.
- Antimony trioxide: probable carcinogen: Sb2O3 dust is classified as a Group 2A probable human carcinogen (IARC); inhalation of the dust or fumes must be controlled with engineering controls and respiratory protection.
- Chronic antimony exposure: Occupational overexposure causes antimoniosis, characterised by dermatitis, respiratory tract irritation, and cardiac arrhythmias; 'antimony spots' on the skin are a characteristic finding.
- Skin and eye irritation: Antimony trichloride and other soluble salts are corrosive to skin and eyes; contact requires immediate washing with water.
Antimony in the Real World
Real-World Uses
- Flame retardant synergist: Antimony trioxide (Sb₂O₃) is used with halogenated flame retardants in plastics, textiles, and rubber to form volatile antimony halides that suppress combustion chain reactions in the gas phase.
- Lead-acid battery plates: Antimony (1–10%) is alloyed with lead in lead-acid battery grids to increase hardness, reduce corrosion at the positive plate, and improve deep-discharge cycle life in industrial and starting batteries.
- Semiconductor dopant: Antimony is an n-type dopant in germanium and silicon semiconductors, used in infrared detectors, power transistors, and the buried collector layers of high-frequency bipolar junction transistors.
- Bearing alloys: Antimony is a component of tin-antimony-lead Babbitt metal (white metal) used in sleeve bearings for large machinery and marine engines; it hardens the tin matrix while maintaining good embeddability.
- Pigments and glassware: Naples yellow (lead antimoniate) was one of the most important yellow pigments in oil painting from the 17th to 19th century; antimony sulfide (Sb₂S₃) is used in ruby-red glass and pyrotechnic glitter compositions.
Downloadable Resources
Free periodic table reference sheets for classrooms, study sessions, and laboratory use.
Frequently Asked Questions
What is antimony used for?
Antimony is used mainly as a flame retardant synergist: antimony trioxide is combined with halogenated flame retardants in plastics, textiles, and rubber to enhance their fire resistance. Antimony is also an alloying component in lead-acid battery grids, where it hardens the lead plates. Historically, antimony trioxide was used as a white pigment, and antimony sulphide is still used in matches.
Is antimony toxic?
Yes, antimony and most of its compounds are toxic. Antimony poisoning causes symptoms very similar to arsenic poisoning, including nausea, vomiting, and in severe cases heart problems. Antimony trioxide is classified as a possible human carcinogen. Historically, antimony potassium tartrate ('tartar emetic') was used as a medicine and emetic, and some historians suspect it may have contributed to Mozart's death.
How was antimony discovered?
Antimony has been known since antiquity: grey antimony sulphide (stibnite) was used as eye cosmetics in ancient Egypt and the Middle East. The metal itself was described in a 1540 treatise attributed to the monk Basil Valentine, though the attribution is disputed. The name antimony may derive from the Greek 'anti monos' (not alone), since it was rarely found as a pure element, or from an Arabic root via Latin 'stibium'.
What is the role of antimony in flame retardants?
Antimony trioxide (Sb2O3) is not a flame retardant on its own: it acts as a synergist with halogenated flame retardants such as brominated or chlorinated compounds. During combustion, antimony reacts with the halogen to form antimony trihalides (e.g., SbBr3), which are dense, reactive vapour-phase species that inhibit the radical chain reactions that sustain flames. The synergistic combination is far more effective than either component alone.