If your heaviest known is Francium at the atomic mass of 87, your next alkali metal will be in period 8, column 1a. To reach period 8 column 1a, you must add 3 protons to the largest known element,(found in period 8 column 6a) which would bring your atomic number to 119. To find out the atomic number of francium, we can use the periodic table. With the help of the periodic table, we can easily see that the atomic number of francium is 87. A radioactive alkali metal with the atomic symbol Fr, and atomic number 87. The mass numbers of known isotopes are 204-213, 217-224. Its valence is +1.The existence of Francium was predicted by Dmitri Mendeleev in the 1870's and he presumed it would have chemical and physical properties similar to Cesium. Numerous historical claims to the discovery of element 87 were made resulting in the names Russium, Virginium, and Moldavium.
This element, which was named for France, was discovered in 1939 by Marguerite Perey, who was an assistant to Marie Curie, at the Curie Institute in Paris. There was a British team working to be the first to discover this element at the same time as a French team. The British team wanted to name the element 'Britium' - the French team discovered it first and named it after their country.
Francium was the last element discovered in nature. Originally named Actinium K, it occurs as a result of Actinium's alpha decay and can be artificially made by bombarding Thorium with protons. It is the heaviest alkali metal, but the next element to be discovered will most likely be an alkali metal even heavier than it.
Francium is a highly radioactive alkali metal that is found in very small amounts in Uranium and Thorium ores. It is also notable for having the lowest electronegativity and electron affinity of all the elements.
Francium is the last of the known alkali metals and does not occur to any significant extent in nature. All known isotopes are radioactive and have short half-lives (21.8 minutes is the longest).
Formula For Francium
Due to the small amounts produced and its short half-life, there are currently no uses for Francium outside of basic scientific research.