Periodic table › Francium
1. Identity and classification
Soft, silvery-white, highly reactive metallic solid that tarnishes rapidly in air
- Name and symbol
- Francium (Francium) · Fr
- Atomic number
- 87
- Relative atomic weight / mass number
- [223]
- Group · period · block
- 1 · 7 · s
- Category
- Alkali Metal
- State near room temperature
- Solid
- Stable isotopes
- No stable isotopes
- CAS number
- 7440-73-5
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
- 87 · 87
- Neutrons in reference isotope
- 136 (223Fr)
- Full electron configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s¹- Abbreviated configuration
[Rn]7s¹- Electrons per shell
- 2, 8, 18, 32, 18, 8, 1
- Listed oxidation states
- +1
- Electronegativity
- 0.7 (Pauling)
- First ionization energy
- 376.293 kJ/mol · 3.9 eV
- Electron affinity
- 45.348 kJ/mol
- Covalent radius
- 260 pm
- van der Waals radius
- 348 pm
Configurations of superheavy elements may include theoretical predictions. Different definitions of atomic radius are not interchangeable.
3. Physical and thermal properties
- Density
- Not established
- Melting point
- 300 K · 26.85 °C · 80.33 °F
- Boiling point
- Not established
- Crystal structure
- BCC
- Specific heat
- 0.14 J/(g·K)
- Thermal conductivity
- 15 W/(m·K)
- Enthalpy of fusion
- 2 kJ/mol
- Enthalpy of vaporization
- 65 kJ/mol
- Magnetic ordering
- Paramagnetic
- 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
Usually forms a +1 cation in ionic compounds.
Selected compounds: FrO / Fr₂O₃ (Oxide) · FrClₙ (Chloride) · FrFₙ (Fluoride)
Reaction reference
Readily oxidized in air; storage excludes air and moisture.
Reacts with water to form hydrogen and an alkaline hydroxide solution; vigor varies with the metal.
5. Isotopes
| Isotope | Status | Natural abundance | Half-life |
|---|---|---|---|
| 223Fr | Radioactive | — | 22.00 m |
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
- 1939 CE
- Scientists associated with discovery
- Marguerite Perey
- Location
- France (Curie Institute, Paris)
- Origin
- Trace Natural / Synthetic
- Listed crustal abundance
- Not established
Minerals and naming reference
Trace decay of ²²⁷Ac in uranium minerals; accelerator synthesis
Named from scientific/historical roots associated with Francium (Fr), discovered or characterized by Marguerite Perey.
7. Applications
Laser-cooled magneto-optical traps studying atomic parity non-conservation and the Standard Model weak nuclear force
Detailed applications by field
- everyday
- Laser-cooled magneto-optical traps studying atomic parity non-conservation and the Standard Model weak nuclear force
- industry
- Used in alkali metal processing, specialized alloys, and chemical manufacturing (Laser-cooled magneto-optical traps studying atomic parity non-conservation and the Standard Model weak nuclear force).
- electronics
- Applied in electronic components, semiconductors, or functional coatings where Francium's electronic structure ([Rn] 7s¹) provides target conductivity.
- medicine
- Restricted to controlled nuclear medicine or fundamental radiochemical research.
- energy
- Utilized in power generation, battery materials, catalysts, or nuclear technology involving Francium.
- aerospace
- High-performance materials, structural alloys, or space instrumentation utilizing Francium.
- agriculture
- Not used in agriculture due to radioactivity or heavy-metal toxicity.
- science
- Spectroscopic standard, crystallography, and quantum chemistry studies of Period 7 s-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.