Francium has the largest atomic diameter and is a very ignoble metal. Its chemical properties are similar to caesium, but it is a bit less reactive. However, it is very difficult to explore, because it is generated only in very small amounts from actinium decay. Its most stable isotope, 223Fr, has a half-life of only 22 minutes. This makes francium the most unstable element of the first 105. It has no applications beyond science. On Earth, francium is slightly more frequent than astatine, it decays to radium.