Element 87 · Alkali metal
Francium (Fr) — Element 87
France
Francium (Fr) is an alkali metal in Period 7, Group 1 of the periodic table with atomic number 87, standard atomic weight [223] u, and ground-state electron configuration [Rn] 7s¹. At standard temperature and pressure it is classified as a solid with 1 valence electron and common oxidation states +1.
Research only — extremely rare
What are the atomic properties and physical constants of Francium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 87
- Standard atomic mass
- [223] u
- Chemical family
- Alkali metal
- Ground-state configuration
- [Rn] 7s¹
- Electrons per shell
- 2, 8, 18, 32, 18, 8, 1
- Valence electrons
- 1
- Common ion charges / oxidation states
- +1
- Phase at STP
- Solid
- Pauling electronegativity
- 0.70 Pauling
- First ionization energy
- 380 kJ/mol
- Atomic radius
- —
- Melting point
- 27 °C
- Boiling point
- 677 °C
- Discovery year
- 1939
- Table coordinate
- Period 7, Group 1
- Radioactivity
- Radioactive (no stable isotopes)
How are electrons arranged across Francium’s shells?
A neutral Francium atom contains 87 electrons distributed across 7 occupied principal energy shells ([Rn] 7s¹). The table below compares Francium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Fr | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 8 e⁻ | 8 e⁻ |
| n = 3 | M | 18 e⁻ | 18 e⁻ |
| n = 4 | N | 32 e⁻ | 32 e⁻ |
| n = 5 | O | 18 e⁻ | 50 e⁻ |
| n = 6 | P | 8 e⁻ | 72 e⁻ |
| n = 7 | Q | 1 e⁻ | 98 e⁻ |
Frequently Asked Questions about Francium (Fr)
What is the atomic mass and atomic number of Francium (Fr)?
Francium (Fr) has atomic number Z = 87 (87 protons in its nucleus) and an IUPAC standard atomic weight of [223] u. It sits in Period 7, Group 1 and is classified as an alkali metal.
What is the ground-state electron configuration of Francium?
The neutral ground-state electron configuration of Francium (Z = 87) is [Rn] 7s¹. Across its 7 occupied principal shells (n = 1 to n = 7), the electrons per shell are 2, 8, 18, 32, 18, 8, 1, with 1 valence electron participating in bonding.
What are the common ion charges and electronegativity of Francium?
Francium commonly forms +1 oxidation states or ion charges in compounds. Its Pauling electronegativity is 0.70 and its first ionization energy is 380 kJ/mol.
When was Francium discovered and what is it used for?
Francium was discovered in 1939 (France). Research only — extremely rare
How does Francium compare to neighboring elements?
Other alkali metal elements: