Earth Metals: Elements of the Third Main Group

All elements of the third main group (boron group or earth metals), with the exception of nihonium, which was first produced about ten years ago, were only discovered in the 19th century. Although aluminum is the most common metal, it remained hidden in elemental form for a long time. Gallium, indium, and thallium, on the other hand, are very rare. The elements of this group change their character partly strongly from semi-metal (boron) over the ubiquitous, metallic aluminum to deep-melting heavy metals (gallium, indium, and thallium) and to a possibly volatile and occasionally anionic metal (nihonium).