What are the chemical properties of Francium
Information about the element: Francium
International name (IUPAC): Francium
Origin: Francium is a radioactive chemical element with the element symbol Fr and the atomic number 87. The element is a metal and is in the 7th period, s-block.
Francium has the most unstable isotopes of all elements up to atomic number 104. Even the longest-lived isotope of francium 223Fr has a half-life of only 21.8 minutes. Because of this property and the lack of an efficient nuclear reaction to produce francium (223Fr is created in 1% when 227Ac), it cannot be produced in bulk. Francium can only be studied as salt in dilute solutions and highly diluted as an amalgam.
Experiments show that francium is a typical alkali metal and is very similar to its lighter homologue cesium. It is positively monovalent in aqueous solution and can be converted to cesium in the form of sparingly soluble salts, e.g. B. as perchlorate, tetraphenylborate and hexachloroplatinate, precipitate.
Importance: french France =
Group: 1 (I A)
Group name: Alkali metals
Oxidation number: 1
Atomic mass [u]: [223,02]
Electronegativity (according to Allred): 0,9
Electronegativity (according to Pauling): 0,7
Physical state (20 ° C): firmly
Density [g / cm2]: 1,87
Radioative: 22 min
Melting temperature [° C]: 27
Boiling temperature [° C]: 677
Crystal structure: cubic - body-centered
- History: In 1871, Dmitri Ivanovich Mendeleev predicted the existence of an element that would occupy the then empty space in his periodic table. He described it as an alkali metal and gave it the name. Before the actual discovery of the francium, there were three events misleadingly labeled the discovery of this element:
In 1925 Dmitri Dobroserdow published a theoretical study in which he made predictions about the atomic weight as well as chemical and physical properties. He called the element russium.
A year later, in 1926, two English chemists observed the spectral lines of the element while studying manganese sulfate. They named the element Virginium.
In 1937, the Romanian Horia Hulubei assumed that he had discovered the element and named it Moldavium. However, none of these discoveries has been confirmed by other scientists.
It was not until 1939 that Marguerite Perey was able to use the element as an isotope 223Fr as a decay product of actinium 227Prove Ac beyond any doubt. It was first called Actinium-K and in 1946 in Francium (from French France, the fatherland of the discoverer). The name was accepted by the International Association of Chemists in 1949.
- Physical Properties: The physical properties are essentially estimates that have been determined by extrapolating the properties of the alkali metals or by model calculations. They should therefore be consumed with great caution. Measurements on solids are due to the small quantities that can be produced (few attograms, ~ 10,000 atoms) and the high level of radioactivity (activity is about 2,000,000 times higher than that of 238Pu: visible quantities would evaporate immediately) mostly impossible with today's technical means.
Occurrence: There is no efficient nuclear reaction to produce francium (223Fr is created in 1% when 227Ac), so it cannot be made in bulk.
Frequency: 1,00 ⋅ 10-21 % (percentage by mass of the earth's shell, i.e. the earth's crust / oceans up to 16 km depth)
Discoverer: Marguerite Perey
- 222Fr (synthetic, radioactive, half-life: 14.2 min, 135 neutrons)
- 223Fr (in traces, radioactive, half-life: 21.8 min, 136 neutrons)
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