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Atomic Number: 87
Atomic Weight: -223.0
Element Type: Alkali Metal
Crystal Structure: Cubic Body Centered
Melting Point: 27.0°C = 80.6°F = 300.15 K
Boiling Point: °C = °F = K
Critical Temp: °C = °F = K
Atomic Radius: Å (Å = Angstrom = 10-10
m)
Covalent Radius: Å
Electronegativity: 0.7
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Discovery
(France) Discovered in 1939 by Mlle. Marguerite Perey of
the Curie Institute, Paris.Francium, the heaviest known
member of the alkali metals series, occurs as a result of
analpha disintegration of actinium. It can also be made
by artificially bombarding thoriumwith protons. While it
occurs naturally in uranium minerals, there is probably
less thanan ounce of francium at any time in the total crust
of the earth. It has the highestequivalent weight of any
element, and is the most unstable of the first 101 elements
ofthe periodic system. Thirty-three isotopes of francium
are recognized. The longest lived223Fr (Ac, K), a daughter
of 227Ac, has a half-life of 22 min. This is the only isotope
offrancium occurring in nature. Because all known isotopes
of francium are highly unstable,knowledge of the chemical
properties of this element comes from radiochemical techniques.No
weighable quantity of the element has been prepared or isolated.
The chemicalproperties of francium most resemble cesium.
Sources
Francium occurs as a result of an alpha disintegration
of actinium. It can be produced by artificially bombarding
thorium with protons. It occurs naturally in uranium minerals,
but there is probably less than an ounce of francium at
any time in the total crust of the earth.
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