Francium (Fr): Electron Configuration, Properties and Uses
Francium (Fr): Electron Configuration, Properties and Uses
Electron configuration [Rn] 7s1 · group 1 · period 7 · Ar [223]
Francium data
- Atomic number
- 87
- Relative atomic mass
- [223]
- Group
- 1
- Period
- 7
- Block
- s
- Category
- Alkali metal
- Electron configuration
- [Rn] 7s1
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1
- Electrons per shell
- 2, 8, 18, 32, 18, 8, 1 (K L M N O P Q)
- Valence electrons
- 1
- Electronegativity (Pauling)
- 0.7
- First ionisation energy
- 3.9 eV
- Atomic radius (van der Waals)
- 348 pm
- State at room temperature
- Solid
- Melting point
- 26.9 °C
- Boiling point
- no data
- Density
- no data
- Common oxidation states
- +1
- Discovered
- 1939
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 32 · O 18 · P 8 · Q 1
Orbital diagram (outer electrons)
About francium
Francium is a chemical element with the symbol Fr and atomic number 87. It is an alkali metal in group 1, period 7, s-block. The element was discovered in 1939. Francium is a solid at room temperature, melting at 26.9 °C.
Francium electron configuration
The electron configuration of francium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1, or in short [Rn] 7s1. Its electrons occupy 7 shells: K = 2, L = 8, M = 18, N = 32, O = 18, P = 8, Q = 1. Francium has 1 valence electron in the Q shell (7s1), which is why it sits in group 1. When it forms cations, electrons leave the outermost subshell first: Fr+ = [Rn] (like radon).
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s2(38) → 4d10(48) → 5p6(54) → 6s2(56) → 4f14(70) → 5d10(80) → 6p6(86) → 7s1(87)
Uses of francium
Francium is used for research only; francium is so rare and short-lived that it is studied only in atomic-physics experiments.
Safety
Francium is radioactive. Using, storing or transporting radioactive material requires a licence from the national regulator (BAPETEN in Indonesia). Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 1
Frequently asked questions
What is the electron configuration of francium?
The electron configuration of francium (Fr, atomic number 87) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s1, or [Rn] 7s1 in short. By shell: 2, 8, 18, 32, 18, 8, 1.
How many valence electrons does francium have?
Francium has 1 valence electron.
Which group and period is francium in?
Francium is in group 1, period 7, s-block.
What is the atomic mass of francium?
Francium has no stable isotope, so the mass number of its longest-lived isotope, [223], is given.
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