Francium (Fr)

From Wikipedia, the free encyclopediaFrancium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon.

Francium in the periodic table

SymbolFr
Atomic number87
Group1
Period7
Blocks
Element categoryAlkali Metal

Physical properties

Phase at STPSolid
Density1.87 g/cm3
Atomic weight223 u
Melting point300 K
26.85 °C
80.33 °F
Boiling point950 K
676.85 °C
1250.33 °F

Atomära egenskaper

Electronegativity (Pauling Scale)0.79
Electron affinity46.89 kJ/mol
Ionization energies
1380 kJ/mol

Electron configuration

Electron configuration1s2 2s2 2p6 3s2 3p6 3d10 4s24p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s1
Electrons per shell2, 8, 18, 32, 18, 8, 1

History

Discovered1939
Discovered byMarguerite Perey