Tin, lead and antimony have been known for thousands of years. Tin was mixed with copper in bronze, an alloy so widely used and so significant in the technological development of humanity that it gave its name to an age. Lead was used nine thousand years ago by the ancient Egyptians in the glazing of pottery; and antimony was used in a Chaldean vase of 4000 BC. All three, and bismuth as well, were known to the alchemists; and lead in particular is famous as the metal which alchemists attempted to turn into gold.
Aluminium was the next of these metals to be discovered, identified by the Swedish chemist, Johann August Arfvedson, in 1817, although its compound, alum, had been used in ancient times as a styptic.
Gallium, indium and thallium were discovered by spectroscopic means, a method first used in 1859. Indium and thallium were identified in the early 1860s, and gallium, the existence of which was predicted by Mendeleyev in 1871, was identified in 1875.
The discovery of radioactivity in 1896 opened the doors to the identification of new radioactive elements, and polonium was duly discovered by the Curies in 1898.
