In 1913, English physicist Henry Moseley transformed our understanding of the elements by organizing them by atomic number, from hydrogen to uranium. However, it soon became obvious that researchers had yet to discover seven completely unknown elements. In this updated and expanded edition of his acclaimed book, Eric Scerri presents the intriguing stories of these elements--protactinium, hafnium, rhenium, technetium, francium, astatine, and promethium. It follows their discoveries through the two world wars, starting with protactinium in 1917 and ending with promethium in 1945. Scerri details the research leading to each discovery, the pivotal experiments, the chemists involved, the properties of each element, and their applications. For example, hafnium alloys, named after Copenhagen (hafnia), have some of the highest boiling points and are used in rocket thrusters like those on the Apollo Lunar Modules. Scerri then examines the integration of twenty-five new elements into the periodic table over the past fifty years and concludes with a new chapter on rare earth elements and the histories of their discoveries. The Second Edition of A Tale of Seven Elements vividly portrays the journey of chemical research, from missteps and disputes to the thrill of discovery, illuminating the researchers behind the elements, as much as their breakthroughs.