Write about Francium atom.

     

Francium is a chemical element with the symbol Fr and atomic number 87.   Prior to its discovery, it was referred to as eka-casesium.  it is extremely radioactive; its most stable isotope, francium-233(originally called actinium K after the natural decay chain it appears in), has a half-life of only 22 minutes.   It is the second-most electropositive element, behind only caesium, and is the second rarest naturally occurring element (after astatine).  The isotopes of francium decay quickly into astainte, radium, and radon.  the electronic structure of a francium atom is [Rn] 7s1, and so the element is calles as an alkali metal.  

     Bulk francium has never been viewed.  Because of the general appearance of the other elements in its periodic table column, it is assumed that francium would appear as a highly reactive metal, if enough could be collected together to be viewed as a bulk solid or liquid.  Obtaining such a sample is highly improbable, since the extreme hear of decay caused by its short half-life would immediately vaporize any viewable quantity of the element.

     Francium was discovered by Marguerite Perey  in France in 1939.  It was the last element first discovered in nature, rather than by synthesis.  Outside the laboratory, francium is extremely rare, with trace amounts found in uranium and thorium ores, where the isotope francium-233 continually forms and decays.  As little as 20-3- g exists at any given time throughout the Earth's crust.  the other isotopes are entirely synthetic.  The largest amount produced in the laboratory was a cluster of more than 300,000 atoms.