Francium

Description

Francium, the heaviest of the alkali metals, had been predicted on theoretical grounds and the properties of its compounds known with reasonable confidence for many years. Nevertheless, it remained on periodic charts only as element 87 until the French scientist, Marguerite Perey, discovered in 1939 that a short-lived isotope of element 87 with mass number 223 results from a-decay of actinium isotope 227, itself a decay product of U2. Actinium normally decays by emission, but 1 % of the actinium atoms undergo a-decay. Her experiments with this isotope were recognized as the first reliable evidence of the existence of element 87 and she chose the name francium in honor of her native France. No long-lived francium has been found in nature.It may be said that francium is not found in nature, since it exists only in short-lived radioactive forms. However, Fr223 is one of the daughter elements of U235 , so it must be considered to have transitory existence naturally, even for a very short life span. From the properties of the known isotopes, there is no reason to believe that a long-lived isotope will ever be found or synthesized.

Physical properties

Francium, a radioactive member of Group 1 (the alkali metals) of the Periodic Table, has an atomic number of 87, an atomic weight of 223, a melting point of 27° and a boiling point of 677°. It has an oxidation state of +1. Over 20 isotopes of francium are known. The longest lived, 223Fr, obtained by a-disintegration of 227Ac (4.95 MeV), has a half-life of 22 min. This is the only isotope of francium that occurs naturally (in uranium minerals). Since there is less than 30g of francium at any time in the total crust of the earth, this element is not considered harmful or dangerous.

Uses

The element francium is far too rare and far too radioactive to have any commercial applications. It does have some rather exotic scientific uses, however. Atoms of francium provide an excellent opportunity to examine many aspects of atomic and nuclear physics and even the theory that unifies the electromagnetic and the weak nuclear force into the electroweak force. Th ese experiments have been dubbed "table-top physics" to distinguish them from high-energy physics carried out in huge particle accelerators spanning vast distances the size of cities.

Chemical Properties

heaviest of the alkali metal family; may exist only as radioactive isotopes; only natural isotope is 223Fr with a half-life of 21min; discovered in 1939 by Mll. M. Perey, Curie Inst., Paris; formed from α-decay of actinium [CRC10] [HAW93]

Chemical Properties

Francium is extremely rare. Because of this, its chemical and physical properties are not well characterized. It has been studied by radiochemical techniques, which show that its most stable state is the ion Fr⁺. Francium is the least electrone

History

The name derives from the country “France”, where the French physicist Marguerite Perey from the Curie Institute in Paris, France discovered it in 1939 in the alpha particle decay of actinium, 227Ac→4 He →223Fr, which was known as actinium-K and has a half-life of 22 minutes. An earlier claim of discovery in 1930 with the element name Virginium was determined to be incorrect. A similar claim for discovery of the element with atomic number 87 and named moldavium was also determined to be incorrect. The longest half-life associated with this unstable element is 22 minute ²²³Fr. 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.

Definition

ChEBI: Francium atom is an alkali metal atom.

Raw materials

Preparation Products