Name: francium
Symbol: Fr
Atomic number: 87
Atomic weight: [ 223 ]
Group in periodic table: 1
Group name: Alkaline metal
Period in periodic table: 7
Block in periodic table: s-block
CAS registry ID: 7440-73-5
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.