Fr
Francium
Element 87 · Alkali metal
Francium (Fr)
Francium is an extremely rare, highly radioactive alkali metal. It was the last element discovered in nature.
- Alkali metal
- Period 7
- Group 1
- s-block
- solid at room temperature
- ☢ Radioactive
Key properties
- Atomic mass
- [223]
- u
- Electron configuration
- [Rn] 7s1
- Melting point
- 26.9 °C
- 300 K
- Boiling point
- 676.9 °C
- 950 K
- Density
- 1.87 g/cm³
- Electronegativity
- 0.7
- Pauling
- Atomic radius
- 348 pm
- van der Waals
- 1st ionisation energy
- 3.9 eV
Compare with every element:Electronegativity chartAtomic radius chartIonisation energy chartDensity chart of the elementsMelting point chartElectron configuration chart
Did you know?
Notable facts about francium
- 01
Perey worked as Marie Curie’s lab assistant and found francium in the decay of actinium.
- 02
Its longest-lived isotope has a half-life of only 22 minutes.
- 03
Probably no more than about 30 grams exist in Earth’s crust at any time.
Applications
What is francium used for?
- Research in atomic physics
History
Discovery & name origin
Atomic structure
Atomic properties
Atomic structure
Atomic properties
- Atomic number
- 87
- Atomic mass
- [223] u
- Group
- 1
- Period
- 7
- Block
- s-block
- 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
- Electronegativity (Pauling)
- 0.7
- Electron affinity
- 0.47 eV
- Atomic radius (van der Waals)
- 348 pm
- Stable isotopes
- None — all isotopes are radioactive
Oxidation states
Highlighted: common oxidation states (+1).
Physical
Physical properties & colour
Physical
Physical properties & colour
- State at 20 °C
- Solid
- Melting point
- 300 K · 26.9 °C · 80.3 °F
- Boiling point
- 950 K · 676.9 °C · 1,250.3 °F
- Density
- 1.87 g/cm³
- Molar heat capacity
- —
- Appearance
- —
- CPK model colour
- Copied
The CPK colour is the convention used for this element’s atoms in molecular models.
FAQ
Francium questions
What is Fr on the periodic table?
Fr is the symbol for francium, element 87 on the periodic table. It sits in group 1, period 7, in the alkali metal category, and has an atomic mass of [223].
What is the atomic number of francium?
Francium has atomic number 87, so every francium atom has 87 protons in its nucleus. Its symbol is Fr and its atomic mass is [223].
Who discovered francium?
Francium was discovered by Marguerite Perey in 1939 (France). The name comes from from France.
What is francium used for?
Francium is used for: research in atomic physics.
Is francium a metal?
Yes. Francium is a alkali metal, one of the metallic elements.
What is the electron configuration of francium?
The electron configuration of francium is [Rn] 7s1. Its 87 electrons are arranged in shells as 2, 8, 18, 32, 18, 8, 1.