Antimony (Sb)
Metalloid
Antimony is a brittle, silvery metalloid known since antiquity — ancient Egyptians darkened their eyes with its sulfide as kohl. Today it mainly serves as a flame-retardant synergist and a hardener for lead.
Position on the periodic table
Atomic properties
| Atomic number | 51 |
|---|---|
| Atomic mass | 121.76 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p3 |
| Noble gas shorthand | [Kr] 4d10 5s2 5p3 |
| Electrons per shell | 2, 8, 18, 18, 5 |
| Valence electrons (outer shell) | 5 |
| Common oxidation states | -3, +3, +5 |
| Electronegativity (Pauling) | 2.05 |
| Covalent radius (approx.) | 139 pm |
| First ionization energy | 834 kJ/mol |
| Electron affinity | 101.1 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 6.697 g/cm³ |
| Melting point | 630.63 °C (903.78 K) |
| Boiling point | 1634.8 °C (1908 K) |
| Appearance | silvery lustrous gray |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of antimony
Antimony's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p3, usually shortened to [Kr] 4d10 5s2 5p3. Its electrons occupy 5 shells (2, 8, 18, 18, 5), placing it in period 5 of the p-block. The 5 outer-shell electrons drive its bonding behaviour. Explore it interactively in the electron configuration calculator.
Uses of antimony
- Flame retardants (antimony trioxide)
- Hardening lead for batteries and ammunition
- PET plastic catalyst
- Semiconductor dopant
Biological role: None — moderately toxic.
Occurrence: Mined mainly as stibnite (Sb₂S₃), largely in China.
Common compounds of antimony
Sb2O3
Antimony trioxide
Sb2S3
Stibnite
History and discovery
Discovered: Known since ancient times — unknown, before 3000 BC. Name origin: Uncertain; the symbol Sb comes from Latin stibium, the ancient eye-cosmetic mineral.
Known as a mineral cosmetic for millennia; described in detail by alchemists from the 1500s onward.
Safety notes
Antimony compounds are toxic in quantity; occupational dust exposure is the main concern.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Antimony
1. What is the chemical symbol of Antimony?
2. What is the atomic number of Antimony?
3. Which category does Antimony belong to?
4. What is the state of Antimony at room temperature?
5. Which period of the periodic table is Antimony in?
Antimony FAQs
What is the atomic number of antimony?
Antimony's atomic number is 51 — every antimony atom has 51 protons in its nucleus.
What is the symbol for antimony?
Sb. Uncertain; the symbol Sb comes from Latin stibium, the ancient eye-cosmetic mineral.
Is antimony a metal, nonmetal, or metalloid?
Antimony is classified as a metalloid — an element with properties between metals and nonmetals.
What state is antimony at room temperature?
At about 25 °C, antimony is a solid. It melts at 630.63 °C.
How many valence electrons does antimony have?
Antimony has 5 electrons in its outer shell (shell pattern: 2, 8, 18, 18, 5).
What is antimony used for?
Key uses include: flame retardants (antimony trioxide); hardening lead for batteries and ammunition; pet plastic catalyst.
Related elements
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