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 – Twisting the Dragon's Tail Uranium – Twisting the Dragon's Tail Uranium – Twisting the Dragon's Tail is a television documentary series about uranium, its history, and its uses. It was produced by Gene Pool Productions for PBS and SBS and premiered on both networks in late July and August 2015. The series was conceived, created, written and directed by Wain Fimeri, was shot in nine countries and is presented by Derek Muller. Derek Muller introduces uranium and its use throughout history. Uranium, originally sourced from pitchblende, became the subject of intense scientific study. Using computer-generated dragons as a metaphor for daughter isotopes, the episode