Here is a new video from us about Radon, including a look at a historic letter and a German cloud chamber! With thanks to the Royal Society and GSI. For those with annotations, the caption at the end for Radon should clearly be Rn, not Ra - sorry! More chemistry at http://www.periodicvideos.com/ Follow us on Facebook at http://www.facebook.com/periodicvideos And on Twitter at http://twitter.com/periodicvideos From the School of Chemistry at The University of Nottingham: http://www.nottingham.ac.uk/chemistry/index.aspx Periodic Videos films are by video journalist Brady Haran: http://www.bradyharan.com/ Brady's other channels include: http://www.youtube.com/sixtysymbols (Physics and astronomy) http://www.youtube.com/numberphile (Numbers and maths) http://www.youtube.com/DeepSkyVideos (Space stuff) http://www.youtube.com/nottinghamscience (Science and behind the scenes) http://www.youtube.com/foodskey (Food science) http://www.youtube.com/BackstageScience (Big science facilities) http://www.youtube.com/favscientist (Favourite scientists) http://www.youtube.com/bibledex (Academic look at the Bible) http://www.youtube.com/wordsoftheworld (Modern language and culture) http://www.youtube.com/PhilosophyFile (Philosophy stuff)