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Francium (Fr)

Francium is a chemical element of the periodic table with chemical symbol Fr and atomic number 87 with an atomic weight of 223 u and is classed as alkali metal and is part of group 1 (alkali metal). Francium is solid at room temperature.

Francium in the periodic table

Atomic number87
Group1 (Alkali metal)
ClassificationAlkali Metal
Color Silver
Number of protons87 p+
Number of neutrons136 n0
Number of electrons87 e-
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.

Physical properties

Phase at STPSolid
Density1.87 g/cm3
Atomic weight223 u

Thermal properties

Melting point300 K
26.85 °C
80.33 °F
Boiling point950 K
676.85 °C
1250.33 °F
Heat of vaporization64 kJ/mol

Atomic properties

Electronegativity (Pauling Scale)0.79
Electron affinity46.89 kJ/mol
Oxidation states+1
(a strongly basic oxide)
Ionization energies
  1. 380 kJ/mol

Electron configuration for francium

Electron configuration
Shorthand configuration
[Rn] 7s1
Electron configuration
Full configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s24p6 4d10 4f14 5s2 5p6 5d10 6s2 6p6 7s1
Electron configuration chart
Electrons per shell2, 8, 18, 32, 18, 8, 1
Valence electrons 1
Valency electrons 1
Bohr model
FranciumElectron shell for Francium, created by Injosoft ABFr
Figure: Shell diagram of Francium (Fr) atom.
Orbital Diagram
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The history of Francium

Discovery and first isolationMarguerite Perey (1939)
Discovery of francium
Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. Prior to its discovery, it was referred to as eka-caesium or ekacaesium because of its conjectured existence below caesium in the periodic table. It was the last element discovered in nature, rather than synthesized, following hafnium and rhenium. Perey named the new isotope actinium-K (it is now referred to as francium-223) and in 1946, she proposed the name catium (Cm) for her newly discovered element, as she believed it to be the most electropositive cation of the elements. Irène Joliot-Curie, one of Perey's supervisors, opposed the name due to its connotation of cat rather than cation; furthermore, the symbol coincided with that which had since been assigned to curium. Perey then suggested francium, after France. This name was officially adopted by the International Union of Pure and Applied Chemistry (IUPAC) in 1949, becoming the second element after gallium to be named after France. It was assigned the symbol Fa, but this abbreviation was revised to the current Fr shortly thereafter.


List of unique identifiers for Francium in various chemical registry databases
CAS Number7440-73-5
ChemSpider ID4886484
EC number-
PubChem CID Number6328145