About

Francium is the second-rarest naturally occurring element, after astatine, and the most electropositive. It is an extremely unstable alkali metal, with a half-life of only 22 minutes for its longest-lived isotope. It is found in trace amounts in uranium ores. Due to its extreme instability and rarity, it has never been viewed in bulk and has no commercial applications, being used only in physics research.

Atomic Properties

Atomic Number87

Atomic Weight223 u

Neutrons (common)136

Electron Configuration[Rn] 7s¹

Full Configuration1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶ 7s¹

Electrons per Shell2, 8, 18, 32, 18, 8, 1

Electronegativity0.7

Electron Affinity46.89 kJ/mol

Oxidation States+1

Covalent Radius260 pm

Ionic Radius180 pm

Periodic Table Position

Group1

Period7

BlockS

Chemical SeriesAlkali metals

Physical Properties

State at STPsolid

Appearancehypothetical silvery-white metallic appearance

Crystal Structurebcc

Magnetic Orderingparamagnetic

Thermal Properties

Melting Point300 K

Boiling Point950 K

Thermal Conductivity15 W/(m·K)

Heat of Fusion2 kJ/mol

Heat of Vaporization65 kJ/mol

Abundance

In Earth's Crust0 ppm

Discovery

Discovered byMarguerite Perey

Discovery Year1,939

Occurrencefrom_decay

CAS Number7440-73-5

Electron Configuration

Energy

↿⇂

1s

↿⇂

2s

↿⇂

2p

↿⇂

3s

↿⇂

3p

↿⇂

4s

↿⇂

3d

↿⇂

4p

↿⇂

5s

↿⇂

4d

↿⇂

5p

↿⇂

6s

↿⇂

4f

↿⇂

5d

↿⇂

6p

↿

7s

5f

6d

7p

Isotopes of Francium

Symbol ▲	Mass (u) ▲	Abundance ▲	Half-life ▲	Decay Mode ▲
²²³Fr	223.019730	Trace	22.00 m	Beta Minus Decay, Alpha Decay