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
Uranium tile still standing from that era by use of a simple geiger counter that readily detects the beta radiation emitted by uranium's ever-present decay chain radio-daughters. In most situations, the radiation exposure is not excessive, but there are some exceptions in which pure uranium oxide [which produces red-orange coloration as a glaze] on bathroom floors can pose a hazard for infants crawling around for hours on end, day after day. ORAU Radioactive Tiles Uranium tile Uranium tiles have been used in the ceramics industry for many centuries, as uranium oxide makes an excellent ceramic glaze, and is reasonably abundant on the