Classical alchemy divided matter into just four elements, although some argued for the recognition of a fifth element. Modern chemistry divides matter into a whole array of elements, commonly known as the periodic table. In this table boron is the fifth element, and it sits right at the intersection of many classes of elements; between the metals and the non-metals; between those with just the right number of electrons for bond formation, and those with far too few; between those that form bonds by sharing electrons, and those that give them away. This dichotomy is apparent throughout the chemistry of boron and produces a wonderful variety of effects. From too little boron harming plants, to too much being toxic, boron inhabits a nuanced position throughout science and history. Examples include its inspired use in glass that led to strategic shortages in World War I, whereas too much of it had the potential to stop nuclear reactors in World War II; boron even featured in the Cold War with a brief boom-and-bust in the development of new high-energy fuels. From superconductors to cancer treatments, boron is anything but boring. Beginning with some basics of chemistry, readers are led on an exciting journey exploring the history of this intriguing element into its modern uses that are all around us.
