Francium


Kossel shell structure of Fr



created by Shae and Melody








   

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Sunday, October 05, 2003
About

 Atomic Number

 87

 Atom Symbol

 Fr

 Atomic Weight

 [223]

 Atomic Configuration

 [Rn]7s1

 Group Number

1

 Group Name

 Alkali metal

 Period Number

 7

 Block

 S-block

 Melting Point

 27.0oC

 Boiling Point

 677.0oC


Francium occurs as a result of a 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.

Posted at 12:00 am by Pyro4Jesus
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History

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 caesium rather closely, he called it eka-caesium. Marguerite Perey noticed an a 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.

Posted at 12:00 am by Pyro4Jesus
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How it's made

The Stony Brook group creates Fr atoms with atomic weight 210, (half-life of 3.2 minutes) by bombarding a gold target with beams of oxygen from the linear accelerator in the basement of the physics building at Stony Brook. The nuclear reaction imbeds the francium atoms deep in the gold target. The atoms diffuse fast to the surface of the gold target and are released as ions. The francium ions are guided by electrostatic lenses until they land into a surface of hot yttrium and become neutral again.  An easy way to remember the nuclear reaction is to think of it as inverse alchemy. We start with gold and oxygen, create francium that later decays into other elements that decay into lead. Our process of turning gold to lead is opposite to the dream of the medieval alchemists!
How It's Done

Posted at 12:00 am by Pyro4Jesus
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Orbitron


Posted at 12:00 am by Pyro4Jesus
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Chemical reactions

Reaction of francium with air

So far as I know, nobody has ever assembled enough francium in one place to know for certain its appearance. It is probably a very soft, easily cut, solid metal, perhaps even a liquid at room temperature. A fresh francium surface would soon tarnish because of reaction with oxygen and moisture from the air. Were francium ever to be burned in air, the result is expected to be francium superoxide, FrO2.

Fr(s) + O2(g) FrO2(s)

Reaction of francium with water

Francium is very scarce and expensive. It is unlikely that anyone has ever reacted the metal with water. However, given that all the other Group 1 elements react to form colourless solutions of the hydroxide and hydrogen gas (H2), it would be strange were francium not to do the same. The resulting solution would be basic because of the dissolved hydroxide. The reaction would probably be faster than that of caesium - in other words dangerously quick.

2Fr(s) + 2H2O(l) 2FrOH(aq) + H2

Reaction of francium with the halogens

So far as I know, nobody has ever assembled enough francium in one place to carry out its reactions with halogens. However one can predict that francium metal would react vigorously with all the halogens to form francium halides. So, it would reacts with fluorine, F2, chlorine, Cl2, bromine, I2, and iodine, I2, to form respectively francium(I) bromide, FrF, francium(I) chloride, FrCl, francium(I) bromide, FrBr, and francium(I) iodide, FrI.

2Fr(s) + F2(g) FrF(s)

2Fr(s) + Cl2(g) FrCl(s)

2Fr(s) + Br2(g) FrBr(s)

2Fr(s) + I2(g) FrI(s)

Reaction of francium with acids

I'm not sure this reaction has ever been done, but one would predict that francium metal will dissolve very readily in dilute sulphuric acid to form solutions containing the aquated Fr(I) ion together with hydrogen gas, H2.

2Fr(s) + H2SO4(aq) 2Fr+(aq) + SO42-(aq) + H2(g)


Posted at 01:00 am by Pyro4Jesus
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