Francium occurs as a result of α
disintegration of actinium. Francium is found in uranium minerals, and can be
made artificially by bombarding thorium with protons. It is the most unstable
of the first 101 elements. The longest lived isotope, 223Fr, a daughter of
227Ac, has a half-life of 22 minutes. This is the only isotope of francium
occurring in nature, but at most there is only 20-30 g of the element present in the earth's
crust at any one time. No weighable quantity of the element has been prepared
or isolated. There are about 20 known isotopes.
•Name: Francium
•Symbol: Fr
•Atomic number: 87
•Atomic weight: [ 223 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-73-5
•Group in periodic table: 1
•Group name: Alkali metal
•Period in periodic table: 7
•Block in periodic table: s-block
•Color: metallic
•Classification: Metallic
Historical information
Francium was discovered in 1939 by Marguerite Perey of the Curie Institute in Paris, (France) but its existence was predicted by Mendeleev during the 1870's. Since its properties should track those of cesium rather closely, he called it eka-cesium. Marguerite Perey noticed an α decay product from actinium, now recognized as ^22387Fr. This is the longest-lived isotope of actinium with a half life of about 22 minutes. She called the new element Francium after her country.
Physical properties
•Melting point: maybe about 300 [or about 30 °C, estimate] K
•Boiling point: 871 [or 598 °C (1108 °F)] K
•Density of solid: 2900 (estimated) kg m-3
Orbital properties
•Ground state electron configuration: [Rn].7s1
•Shell structure: 2.8.18.32.18.8.1
•Term symbol: 2S1/2
•Pauling electronegativity: 0.7 (Pauling units)
• First ionisation energy: 380 kJ mol-1
• Second ionisation energy: no data kJ mol-1
Isolation
Francium is vanishingly rare and is found only as very small traces in some uranium minerals. It has never been isolated as the pure element. As it is so radioactive, any amount formed would decompose to other elements.
Actinium decays by β decay most of the time but about 1% of the decay is by α decay. The "daughter" element of this reaction, which used to be called actinium-K, is now recognized as 22387Fr - the longest-lived isotope of actinium with a half life of about 22 minutes.
•Name: Francium
•Symbol: Fr
•Atomic number: 87
•Atomic weight: [ 223 ]
•Standard state: solid at 298 K
•CAS Registry ID: 7440-73-5
•Group in periodic table: 1
•Group name: Alkali metal
•Period in periodic table: 7
•Block in periodic table: s-block
•Color: metallic
•Classification: Metallic
Historical information
Francium was discovered in 1939 by Marguerite Perey of the Curie Institute in Paris, (France) but its existence was predicted by Mendeleev during the 1870's. Since its properties should track those of cesium rather closely, he called it eka-cesium. Marguerite Perey noticed an α decay product from actinium, now recognized as ^22387Fr. This is the longest-lived isotope of actinium with a half life of about 22 minutes. She called the new element Francium after her country.
Physical properties
•Melting point: maybe about 300 [or about 30 °C, estimate] K
•Boiling point: 871 [or 598 °C (1108 °F)] K
•Density of solid: 2900 (estimated) kg m-3
Orbital properties
•Ground state electron configuration: [Rn].7s1
•Shell structure: 2.8.18.32.18.8.1
•Term symbol: 2S1/2
•Pauling electronegativity: 0.7 (Pauling units)
• First ionisation energy: 380 kJ mol-1
• Second ionisation energy: no data kJ mol-1
Isolation
Francium is vanishingly rare and is found only as very small traces in some uranium minerals. It has never been isolated as the pure element. As it is so radioactive, any amount formed would decompose to other elements.
Actinium decays by β decay most of the time but about 1% of the decay is by α decay. The "daughter" element of this reaction, which used to be called actinium-K, is now recognized as 22387Fr - the longest-lived isotope of actinium with a half life of about 22 minutes.
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