Period 7 element elements of the 7th period. Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K. It is one of the two least electronegative elements, the other being caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon. As an alkali metal, it has one valence electron. Francium was discovered by Marguerite Perey in France (from which the element takes its name) in 1939. It was the last element discovered in nature, rather than by synthesis. Outside the laboratory, francium is extremely rare, with trace amounts
Bioremediation of radioactive waste acids and siderophores that allow the dissolution and mobilization of radionuclides through the soil. It seems that siderophores on bacterial surface could also facilitate the entry of these elements within the cell as well. "Pseudomonas aeruginosa" also secretes chelating agents out that meet uranium and thorium when grown in a medium with these elements. In general, it has also been found that enterobactin siderophores are extremely effective in solubilizing actinide oxides of plutonium. Citrate is a chelator which binds to certain transition metals and radioactive actinides. Stable complexes such as bidentate, tridentate (ligands with more than one atom bound) and