Period 6 element the last stable element; all subsequent elements are radioactive. For bismuth, however, its only primordial isotope, Bi, has a half-life of more than 10 years, over a billion times longer than the current age of the universe. As a rule, period 6 elements fill their 6s shells first, then their 4f, 5d, and 6p shells, in that order; however, there are exceptions, such as gold. This period contains the lanthanides, also known as the "rare earths". Many lanthanides are known for their magnetic properties, such as neodymium. Many period 6 transition metals are very valuable, such as gold, however many
Minor metals Minor metals Minor metals is a widely used term in the metal industry that generally refers to metals which are a by-product of smelting a base metal. Minor metals do not have a real exchange, and are not traded on the London Metal Exchange (LME). Two characteristics are regularly associated with minor metals: (1) their global production is relatively small in comparison to base metals, and (2), they are predominantly extracted as by-products of base metals. However, due to the diversity of the metals often classified as minor metals, there is still much discussion about what exactly defines a minor