Then and Now - The Periodic Table Element - Dysprosium. Dysprosium, an element with the atomic number 66, is a rare-earth metal known for its unique magnetic properties. Discovered in 1886 by French chemist Paul Émile Lecoq de Boisbaudran, dysprosium was initially hailed as a revolutionary element with promising applications across multiple industries. However, over time, its extensive use has diminished for several reasons. This article explores the early uses of dysprosium and delves into the factors that led to its decline in those areas. Read more.