Francium
The second-rarest element, an extremely unstable alkali metal.
Inside the Francium atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Francium atom step by step.
Electron configuration
[Rn] 7s1
A neutral Francium atom has 87 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 300 K (27 °C)
- Boiling point
- 950 K (677 °C)
- Density
- —
- Electronegativity
- 0.7 Pauling
- Atomic radius
- 260 pm
- 1st ionization energy
- 380 kJ/mol
- Category
- Alkali metals
Discovery & naming
- Discovered
- 1939
- Discovered by
- Marguerite Perey
- Origin of name
- France, the discoverer's homeland.
Notable uses
Scientific research only; no commercial use.
Where Francium comes from
Neutron star mergers
Occurs on Earth only as a fleeting decay product of uranium and thorium, so it inherits their r-process origin.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 87
- Atomic mass
- [223]
- Category
- Alkali metals
- Group · Period
- 1 · 7
- Block
- s-block
- Shells
- 2 · 8 · 18 · 32 · 18 · 8 · 1