What is Francium?
{{Infobox francium}}'''Francium''' is a [[chemical element]] with the chemical symbol '''Fr''' and an [[atomic number]] of 87. It is a [[metal]]. In chemistry it is placed in a group of metal elements named the [[alkali metal]]s. Francium is very [[radioactive]]. It is in very small amounts in [[uranium]] and [[thorium]] [[ore]]s. It has the lowest [[electronegativity]] and [[electron affinity]] of all the chemical elements. Francium reacts violently with water, as do all of the elements in group 1 on the periodic table. Francium is one of the hardest to find elements on the planet [[Earth]]. It is estimated that there are only about 15&nbsp;grams or half an ounce in the Earth's [[crust (geology)|crust]] at a single time.<ref name = Advameg>{{cite web|url = http://www.chemistryexplained.com/elements/C-K/Francium.html|title = Francium, Chemical Element |work = Chemistry: Foundations and Applications - Elements|publisher = Advameg, Inc|accessdate = 2008-11-21}}</ref> Although chemists knew the element number 87 in the [[periodic table]] should exist, it was a long time before it was discovered. In the early 1900s, nearly all boxes on the periodic table had been filled. [[Chemist]]s knew that one element had been found to fit into each box. Francium was discovered in 1939 by a [[French people|French]] chemist called [[Marguerite Perey]].<ref name = Advameg/> She named it after her home country, France. ==Isotopes== There are 34 known isotopes of francium ranging in [[atomic mass]] from 199 to 232. Francium-223 and francium-221 are the only isotopes that occur in nature. Francium-223 is the most stable [[isotope]], with a half-life of 21.8 minutes. Francium-223 is the fifth product of the actinium decay series as the daughter isotope of actinium-227. Francium-223 then decays into radium-223 by [[beta decay]] (1.149 MeV decay energy), with a minor (0.006%) [[alpha decay]] path to astatine-219 (5.4 MeV decay energy). Francium-221 has a half-life of 4.8 minutes. It is the ninth product of the neptunium deca