Group 12 element people in the 17th century. German chemist Andreas Marggraf is usually given credit for discovering pure metallic zinc in a 1746 experiment by heating a mixture of calamine and charcoal in a closed vessel without copper to obtain a metal. Experiments on frogs by the Italian doctor Luigi Galvani in 1780 with brass paved the way for the discovery of electrical batteries, galvanization and cathodic protection. In 1880, Galvani's friend, Alessandro Volta, invented the Voltaic pile. The biological importance of zinc was not discovered until 1940 when carbonic anhydrase, an enzyme that scrubs carbon dioxide from blood, was shown to
Group 6 element principal ore from which molybdenum is now extracted—was previously known as molybdena, which was confused with and often implemented as though it were graphite. Like graphite, molybdenite can be used to blacken a surface or as a solid lubricant. Even when molybdena was distinguishable from graphite, it was still confused with a galena (a common lead ore), which took its name from Ancient Greek "", meaning "lead". It was not until 1778 that Swedish chemist Carl Wilhelm Scheele realized that molybdena was neither graphite nor lead. He and other chemists then correctly assumed that it was the ore of a