Periodic table › Astatine
1. Identity and classification
Colored, pungent, reactive diatomic nonmetal (gas, volatile liquid, or crystalline solid)
- Name and symbol
- Astatine (Astatine) · At
- Atomic number
- 85
- Relative atomic weight / mass number
- [210]
- Group · period · block
- 17 · 6 · p
- Category
- Halogen
- State near room temperature
- Solid
- Stable isotopes
- No stable isotopes
- CAS number
- 7440-68-8
Square brackets [A] indicate a representative isotope mass number, not an average atomic weight. Neutron counts differ between isotopes.
2. Atomic structure and electron configuration
- Protons · electrons in a neutral atom
- 85 · 85
- Neutrons in reference isotope
- 125 (210At)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s² 5p⁶ 4f¹⁴ 5d¹⁰ 6s² 6p⁵- Abbreviated configuration
[Xe]6s² 4f¹⁴ 5d¹⁰ 6p⁵- Electrons per shell
- 2, 8, 18, 32, 18, 7
- Listed oxidation states
- 7, 5, 3, 1, -1
- Electronegativity
- 2.2 (Pauling)
- First ionization energy
- 916.611 kJ/mol · 9.5 eV
- Electron affinity
- 270.159 kJ/mol
- Covalent radius
- 150 pm
- van der Waals radius
- 202 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- 7 g/cm³
- Melting point
- 575 K · 301.85 °C · 575.33 °F
- Boiling point
- Not established
- Crystal structure
- FCC
- Specific heat
- 0.14 J/(g·K)
- Thermal conductivity
- 1.7 W/(m·K)
- Enthalpy of fusion
- 6 kJ/mol
- Enthalpy of vaporization
- 40 kJ/mol
- Magnetic ordering
- Diamagnetic
- Mohs hardness
- Not established
- Speed of sound
- Not established
Density and structure depend on temperature, pressure and allotrope. 25°C is a room-temperature reference, not STP. Unestablished values are not zero.
4. Chemical behavior and compounds
The listed electron configuration and oxidation states describe atomic structure; compound properties depend on bonding and composition.
Selected compounds: AtO / At₂O₃ (Oxide) · AtClₙ (Chloride) · AtFₙ (Fluoride)
Reaction reference
Oxidation behavior depends on temperature, surface passivation and the chemical environment.
Direct reaction with water is element- and condition-dependent.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 210At | Radioactive | — | 8.1 h |
Half-life units: s seconds, m minutes, h hours, d days, Y years. A dash means no natural-abundance value is given, not zero. Listed records are selected ground states; metastable states are distinct.
6. Discovery and occurrence
- Discovery
- 1940 CE
- Scientists associated with discovery
- Dale R. Corson, Kenneth Ross MacKenzie & Emilio Segrè
- Location
- USA (UC Berkeley)
- Origin
- Trace Natural / Synthetic
- Listed crustal abundance
- Not established
Minerals and naming reference
Trace in Uranium/Thorium decay chains (<1 gram in Earth's crust at any moment); cyclotron synthesis via ²⁰⁹Bi(α,2n)²¹¹At
Named from scientific/historical roots associated with Astatine (At), discovered or characterized by Dale R. Corson, Kenneth Ross MacKenzie & Emilio Segrè.
7. Applications
Astatine-211 (²¹¹At) targeted alpha-particle radioimmunotherapy for micrometastatic cancers
Detailed applications by field
- everyday
- Astatine-211 (²¹¹At) targeted alpha-particle radioimmunotherapy for micrometastatic cancers
- industry
- Used in halogen processing, specialized alloys, and chemical manufacturing (Astatine-211 (²¹¹At) targeted alpha-particle radioimmunotherapy for micrometastatic cancers).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Astatine's electronic structure ([Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁵) provides target conductivity.
- medicine
- Diagnostic imaging, biomedical instrumentation, or pharmaceutical synthesis research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Astatine.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Astatine.
- agriculture
- Not used in agriculture due to radioactivity or heavy-metal toxicity.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 6 p-block elements.
8. Biological role and safety
Hazard depends on the isotope, chemical form, dose and exposure route.
Elemental substances, ions, compounds and radioisotopes can have different health effects. This is an educational reference; laboratory work requires the material safety data sheet and trained supervision.
Biological role reference
Classified as highly radioactive / synthetic in human and biological systems.