51 Sb Antimony 121.76
Metalloid p-block Period 5 Group 15

Antimony

Sb · Element 51 · Pnictogens

A brittle metalloid used since antiquity as eye cosmetic, and now as a flame retardant.

STATE AT 20°C Solid
ATOMIC MASS 121.76 u
ELECTRON CONFIGURATION [Kr] 4d¹⁰ 5s² 5p³
50Sn All 118 52Te

Structure

The antimony atom

Not a diagram of dots on rings — a Monte-Carlo sample of the actual probability density |ψ|² for each occupied subshell. Drag to rotate. Blue and violet mark opposite signs of the wavefunction, which is what makes bonding possible.

Orbital cloud

Measured values

Property sheet

Every bar shows where antimony sits among all 118 elements for that property.

Physical

Density 6.697 g/cm³ 38%
Melting point 903.8 K 37%
Boiling point 1860 K 42%
Specific heat 0.207 J/g·K
Thermal conductivity 24.3 W/m·K 55%

Atomic

Atomic radius 139 pm 30%
Covalent radius 139 pm
Van der Waals radius 206 pm

Electronic

Electronegativity 2.05 73%
Ionisation energy 833.6 kJ/mol 73%
Electron affinity 101.3 kJ/mol 76%

Occurrence

Abundance in crust 0.2 mg/kg 44%

Identity

SymbolSb
Atomic number51
Atomic mass121.76 u
CategoryMetalloid
Blockp
Crystal structurerhombohedral
Oxidation states-3, +3, +5
Discoveredancient
Discovered byKnown since antiquity

Sources: IUPAC 2021 standard atomic weights · CRC Handbook of Chemistry and Physics · NIST. Values marked ~ are predicted rather than measured.

Size, to scale

How big is an antimony atom?

Radius 139 pm — that is 0.139 nm, so about 3597 million of them side by side would span a millimetre.

Thermal range

Solid, liquid, gas — and when

Antimony is liquid over a 956 K window, from 904 K to 1860 K.

Where it sits

Position in the table

Antimony sits in period 5, group 15. Everything in group 15 shares the same outer-electron count, which is why they behave so similarly.

OTHER METALLOIDS

5B 14Si 32Ge 33As 52Te 85At
All metalloids

The story

What antimony is, and how we found it

A brittle metalloid used since antiquity as eye cosmetic, and now as a flame retardant.

The discovery of antimony

Ancient Beauty Secret to Modern Element

Ancient Egyptian Origins (3000 BCE)

Antimony's story begins with ancient beauty rituals. Egyptian queens, including Cleopatra, used ground stibnite (antimony sulfide) as "kohl" - dramatic black eye makeup that also protected against eye infections and glare from desert sun.

"Her eyes were lined with kohl made from stibnite, giving her a gaze that could command empires." - Ancient description of Egyptian beauty

Medieval Alchemy

Medieval alchemists called antimony "the wolf of metals" because it seemed to "devour" other metals when heated together. The symbol ♁ represented antimony in alchemical texts, and practitioners believed it held transmutation powers.

The Monk's Mysterious Discovery

Around 1450, a German Benedictine monk named Basil Valentine (possibly a pseudonym) wrote extensively about antimony in his manuscript "The Triumphal Chariot of Antimony." He described methods for extracting metallic antimony and its medical applications - though his treatments often proved toxic.

Noble Metal Confusion

For centuries, antimony was confused with lead and tin. The name comes from Greek "anti-monos" meaning "not alone" because it was rarely found in pure form. Arabic alchemists called it "al-ithmid," later corrupted to "antimony."

Scientific Recognition

Nicolas Lémery (1707) first clearly distinguished antimony as a distinct element in his chemical treatise. He demonstrated that antimony could be isolated as a brittle, silvery metal with unique properties different from lead or tin.

Industrial Revolution Applications

The Industrial Revolution revealed antimony's true potential:

  • 1780s: Type metal alloys for printing presses revolutionized publishing
  • 1840s: Antimony in friction matches and percussion caps
  • 1860s: Britannia metal (antimony-tin alloy) for decorative items
  • 1890s: Lead-antimony battery grids developed for early automobiles

20th Century Flame Retardant Revolution

1950s Discovery: Scientists discovered that antimony trioxide dramatically enhanced the flame-retardant properties of halogenated compounds. This breakthrough led to antimony's most important modern application - saving countless lives through fire prevention.

Modern Understanding

Today we understand antimony as a metalloid with unique properties:

  • Electron Configuration: [Kr] 4d¹⁰ 5s² 5p³
  • Allotropy: Exists in multiple crystalline forms
  • Semiconductor Properties: Used in modern electronics and infrared detectors
Amazing Journey: From Cleopatra's eye makeup to modern fire safety - antimony's 5,000-year journey shows how ancient materials can find revolutionary new purposes through scientific understanding!

Applications

What antimony is used for

Fire Safety & Flame Retardants

Antimony trioxide (Sb₂O₃) is the world's most important flame retardant synergist, used in over 60% of global antimony consumption. It works by releasing antimony halides that interfere with combustion chemistry, protecting everything from children's pajamas to aircraft interiors.

Automotive Industry

  • Brake Pads: Antimony sulfide provides friction material that performs consistently at high temperatures
  • Battery Grids: Lead-antimony alloys (2-6% Sb) in car batteries provide mechanical strength and corrosion resistance
  • Bearing Alloys: Antimony-tin-copper Babbitt metals for heavy-duty engine bearings
  • Soldering: Antimony in lead-free solders for automotive electronics

Glass & Ceramics

  • Glass Clarification: Antimony trioxide removes bubbles and improves clarity in high-quality glass production
  • Decolorizing Agent: Neutralizes yellow and green tints caused by iron impurities in glass
  • Opacifying Agent: Creates white, opaque glass and ceramic glazes
  • Television Screens: Antimony compounds in cathode ray tube glass for radiation shielding

Textiles & Plastics

  • Polyester Production: Antimony catalysts (antimony trioxide) enable polyethylene terephthalate (PET) polymerization
  • Flame-Retardant Fabrics: Antimony compounds in carpets, upholstery, and protective clothing
  • Plastic Additives: Antimony trioxide combined with halogenated compounds in rigid PVC and thermoset plastics

Pigments & Paints

  • Naples Yellow: Lead antimonate creates this historic artistic pigment used since ancient times
  • Camouflage Paints: Antimony compounds reduce infrared reflectance for military applications
  • Ceramic Glazes: Antimony creates yellow and white colors in pottery and tiles

Electronics & Semiconductors

  • Semiconductor Doping: Ultra-pure antimony as n-type dopant in silicon and germanium
  • Thermoelectric Devices: Bismuth-antimony alloys for Peltier cooling systems
  • Infrared Detectors: Indium antimonide (InSb) for military and scientific applications
  • Diodes: Antimony compounds in tunnel diodes and microwave devices

Military & Defense

  • Tracer Ammunition: Antimony compounds create visible bullet trajectories
  • Primer Compositions: Antimony trisulfide in percussion caps and small arms primers
  • Armor Piercing: Antimony hardens lead cores in armor-piercing projectiles

Pharmaceutical Applications

  • Antiparasitic Drugs: Antimony compounds treat leishmaniasis and schistosomiasis
  • Veterinary Medicine: Antimony potassium tartrate for treating certain animal parasites

Everyday Antimony

Fire Safety in Your Home

  • Mattresses: Antimony-based flame retardants in foam and fabric covers
  • Carpets & Rugs: Antimony trioxide prevents rapid fire spread in home furnishings
  • Children's Clothing: Flame-retardant sleepwear uses antimony compounds for safety
  • Upholstery: Sofas, chairs, and curtains treated with antimony-based fire retardants
  • Electronics Casings: TV, computer, and appliance housings contain antimony for fire safety

Your Vehicle

  • Car Battery: Lead-antimony grids provide structure and longevity
  • Brake Pads: Antimony sulfide friction material stops your car safely
  • Interior Components: Dashboard plastics and seat fabrics with flame retardants
  • Electronic Systems: Antimony in solder joints and semiconductor components

Food & Beverage Containers

  • Plastic Bottles: Antimony catalysts used in PET bottle production (water, soda bottles)
  • Food Packaging: Polyester films and containers made with antimony catalysts
  • Microwave Containers: Heat-resistant plastics often contain antimony compounds

Clothing & Textiles

  • Polyester Clothing: Nearly all polyester fabric made using antimony catalysts
  • Carpet Backing: Antimony in synthetic carpet fibers and backing materials
  • Sports Equipment: Antimony in flame-resistant athletic wear and equipment

Construction Materials

  • Insulation: Antimony-treated foam insulation for fire safety compliance
  • Electrical Wiring: Antimony in PVC wire coatings for flame resistance
  • Roofing Materials: Antimony compounds in synthetic roofing membranes

Consumer Electronics

  • Circuit Boards: Antimony in flame-retardant PCB substrates
  • Cable Sheathing: Antimony-treated plastic covering on electrical cables
  • Device Housings: Antimony fire retardants in phone and computer cases
Hidden Antimony: You interact with antimony dozens of times daily without knowing it - from your polyester shirt to your car's brake pads to your water bottle. It's one of chemistry's most invisible but essential elements!

Where it comes from

Natural occurrence

0.2 mg/kg of Earth's crust · more abundant than 44% of elements

Global Antimony Distribution

Primary Mineral: Stibnite

Stibnite (Sb₂S₃) contains 71.4% antimony and forms distinctive metallic gray crystals with perfect cleavage. Ancient civilizations knew stibnite as "kohl" for eye makeup, not realizing they were using antimony sulfide.

Major Global Deposits

  • China: Dominates with 60% of world production, primarily from Hunan Province's Xikuangshan deposit - the world's largest antimony mine
  • Russia: Significant deposits in Siberia, particularly the Sarylakhskoye deposit
  • Tajikistan: The Zeravshan gold-antimony belt contains major stibnite deposits
  • Myanmar: Historic antimony mining region with rich stibnite veins
  • Bolivia: High-altitude deposits in the Andes, often associated with tin and silver
  • Turkey: Important European source with multiple active antimony mines

Geological Formation

Antimony deposits form through hydrothermal processes at relatively low temperatures (150-300°C). The element concentrates in:

  • Epithermal veins: Near-surface deposits formed by hot springs and geothermal activity
  • Replacement deposits: Antimony minerals replacing limestone and other carbonate rocks
  • Polymetallic deposits: Often found with gold, silver, mercury, and arsenic
  • Hot spring deposits: Modern antimony precipitation in active geothermal areas

Associated Minerals

  • Stibiconite (Sb₂O₄): Yellow antimony oxide from stibnite weathering
  • Valentinite (Sb₂O₃): White antimony oxide in oxidized zones
  • Cervantite (Sb₂O₄): Yellow to brown oxidation product
  • Native antimony: Rare metallic antimony in some deposits
  • Tetrahedrite: Copper-antimony sulfide "gray copper ore"

Abundance & Rarity

Antimony ranks as the 63rd most abundant element in Earth's crust at approximately 0.2 ppm, making it rarer than tin but more abundant than silver. Its concentration requires specific geological conditions, making economic deposits uncommon.

Secondary Sources

  • Lead Battery Recycling: Significant antimony recovery from old car batteries
  • Flame Retardant Recycling: Antimony recovery from electronic waste
  • Bearing Metal Recycling: Reclaimed antimony from industrial machinery
Geological Insight: Antimony's tendency to form near active geothermal systems means many deposits occur in volcanic regions - connecting this ancient element to Earth's ongoing geological processes!

Handling

Safety

Antimony Safety Profile

Toxic Metal - Handle with Caution

Antimony and its compounds are toxic and require careful handling. Unlike tin, antimony poses significant health risks through inhalation, ingestion, and skin contact. The toxicity varies greatly between different antimony compounds.

Respiratory Hazards

  • Acute Exposure: Antimony dust and fumes cause pneumoconiosis ("antimony lung")
  • Chronic Effects: Long-term inhalation leads to respiratory irritation and lung scarring
  • Occupational Limit: OSHA limit of 0.5 mg/m³ for workplace air
  • Protective Equipment: Respirators required in industrial settings

Systemic Health Effects

  • Cardiovascular: High doses affect heart rhythm and blood pressure
  • Gastrointestinal: Nausea, vomiting, and diarrhea from acute exposure
  • Skin Effects: "Antimony spots" - pustular skin lesions from contact
  • Reproductive: Some antimony compounds affect fertility and development

Workplace Safety

  • Engineering Controls: Local exhaust ventilation for antimony processing
  • Personal Protection: Gloves, safety glasses, and appropriate respirators
  • Hygiene Practices: Thorough handwashing and separate work clothing
  • Medical Monitoring: Regular health surveillance for exposed workers

Environmental & Consumer Safety

  • Drinking Water: EPA maximum of 6 ppb antimony in drinking water
  • PET Bottles: Trace antimony migration from plastic bottles is generally safe
  • Food Contact: Antimony levels in food are typically very low
  • Electronic Waste: Proper disposal prevents antimony contamination

Fire & Chemical Hazards

  • Stibine Gas (SbH₃): Extremely toxic antimony hydride gas
  • Combustion Products: Burning antimony compounds release toxic fumes
  • Chemical Reactivity: Some antimony compounds are oxidizing agents

Emergency Response

  • Inhalation: Remove to fresh air, seek immediate medical attention
  • Skin Contact: Wash thoroughly with soap and water
  • Eye Contact: Flush with water for 15 minutes, seek medical care
  • Ingestion: Do not induce vomiting, contact poison control
Important: While antimony in consumer products (flame retardants, PET bottles) poses minimal risk, industrial antimony requires strict safety protocols. Always follow MSDS guidelines when working with antimony compounds.

Quick answers

Antimony: common questions

What is Antimony?

Antimony (symbol Sb) is element 51 on the periodic table, a metalloid in period 5, group 15. A brittle metalloid used since antiquity as eye cosmetic, and now as a flame retardant. At room temperature it is a solid.

What is the electron configuration of Antimony?

Antimony's ground-state electron configuration is [Kr] 4d¹⁰ 5s² 5p³, giving 5 occupied shells holding 2, 8, 18, 18, 5 electrons respectively. Its outer shell holds 5 electrons, which is what sets its bonding behaviour.

What are the melting and boiling points of Antimony?

Antimony melts at 903.8 K (630.6 °C) and boils at 1860 K (1586.9 °C).

What is the atomic mass of Antimony?

The standard atomic weight of Antimony is 121.76 u. That is a weighted average across its naturally occurring isotopes, which is why it is rarely a whole number.

How dense is Antimony?

Antimony has a density of 6.697 g/cm³. Water is 1.0 g/cm³, so a block of antimony is about 6.7× heavier.

What is the electronegativity of Antimony?

Antimony has a Pauling electronegativity of 2.05. The scale runs from 0.70 (francium, the least greedy for electrons) to 3.98 (fluorine, the most). Values in this middle band tend to form covalent rather than strongly ionic bonds.

Who discovered Antimony, and when?

Antimony has been known since antiquity — it occurs in a form usable without smelting, so no single person can be credited with its discovery. The name comes from greek anti + monos; symbol from stibium.

How common is Antimony on Earth?

Antimony makes up about 0.2 mg/kg of the Earth's crust — genuinely rare, which is why it is expensive.

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