Francium (Fr)
Isotopes of Francium
| Isotope | Atomic Mass | Half-life | Mode of Decay | Nuclear Spin |
| Fr-210 | 209.99640 | 3.20 minutes | α to At-206; EC to Rn-210 | 6 |
| Fr -211 | 210.99553 | 3.10 minutes | α to At-207; EC to Rn-211 | 9/2 |
| Fr-212 | 211.99618 | 20 minutes | α to At-208; EC to Rn-212 | 5 |
| Fr-213 | 212.99617 | 34.60 seconds | α to At-209; EC to Rn-213 | 9/2 |
| Fr-214 | 213.99895 | 0.0051 seconds | α to At-210 | 1 |
| Fr-215 | 215.00033 | 0.0000012 seconds | α to At-211 | 9/2 |
| Fr-216 | 216.00319 | 0.000007 seconds | α to At-212; EC to Rn-216 | No data available |
| Fr-217 | 217.00462 | 0.00016 seconds | α to At-213 | 9/2 |
| Fr-218 | 218.00756 | 0.001 seconds | α to At-214 | 1 |
| Fr-219 | 219.00924 | 0.021 seconds | α to At-215 | 9/2 |
| Fr-220 | 220.01231 | 27.40 seconds | α to At-216; β- to Ra-220 | 1 |
| Fr-221 | 221.01425 | 4.80 minutes | α to At-217; β- to Ra-221; C-14 | 5/2 |
| Fr-222 | 222.01754 | 14.30 minutes | β- to Ra-222 | 2 |
| Fr-223 | 223.019733 | 22 minutes | α to At-219; β- to Ra-223 | 3/2 |
| Fr-224 | 224.02323 | 3 minutes | β- to Ra-224 | 1 |
| Fr-225 | 225.02561 | 3.90 minutes | β- to Ra-225 | 3/2 |
| Fr-226 | 226.0293 | 49 seconds | β- to Ra-226 | 1 |
| Fr-227 | 227.0318 | 2.48 minutes | β- to Ra-227 | 1/2 |
Francium was discovered in 1939 by Marguerite Perey. It is named for France, where it was discovered. Its existence had been predicted during the 1870s by Mendeleev, who named it "eka-caesium," correctly predicting that its properties would resemble those of cesium.
Francium is the most unstable of the naturally-occurring elements. No weighable amount has ever been prepared. Preparing such a sample would be impossible, since the extreme heat of decay (the half-life of its longest-lived isotope is only 22 minutes) would immediately vaporize any viewable quantity of the element.
Due to its instability and rarity, there are no commercial applications for francium. It has been used for research purposes in the fields of biology and atomic structure. Its use as a potential diagnostic aid for various cancers has also been explored, but this application has been deemed impractical.
Properties of Francium
| Name | Francium |
| Symbol | Fr |
| Atomic number | 87 |
| Atomic weight | 223 |
| Standard state | Solid at 298 °K |
| CAS Registry ID | 7440-73-5 |
| Group in periodic table | 1 |
| Group name | Alkali metal |
| Period in periodic table | 7 |
| Block in periodic table | s-block |
| Color | Metallic |
| Classification | Metallic |
| Melting point | 30 °C |
| Boiling point | 598 °C |
| Thermal conductivity | 15 (estimate) W/(m·K) |
| Electronegativity | 0.7 |
| Heat of vaporization | About 65 kJ·mol-1 |
| Heat of fusion | About 2 kJ·mol-1 |
| Density of solid | 2.9 (estimated) g/cm3 |
| Electron configuration | [Rn]7s1 |
| Oxidation state | +1 |
