Group 12 element have zinc in its active site. In 1817, cadmium was discovered in Germany as an impurity in zinc carbonate minerals (calamine) by Friedrich Stromeyer and Karl Samuel Leberecht Hermann. It was named after the Latin "cadmia" for "calamine", a cadmium-bearing mixture of minerals, which was in turn named after the Greek mythological character, Κάδμος Cadmus, the founder of Thebes. Stromeyer eventually isolated cadmium metal by roasting and reduction of the sulfide. In 1927, the International Conference on Weights and Measures redefined the meter in terms of a red cadmium spectral line (1 m = 1,553,164.13 wavelengths). This definition has since
Period 6 element in 1839 as an impurity in cerium nitrate – hence the name "lanthanum", from the Ancient Greek "λανθάνειν" ("lanthanein"), meaning "to lie hidden". Although it is classified as a rare earth element, lanthanum is the 28th most abundant element in the Earth's crust, almost three times as abundant as lead. In minerals such as monazite and bastnäsite, lanthanum composes about a quarter of the lanthanide content. It is extracted from those minerals by a process of such complexity that pure lanthanum metal was not isolated until 1923. Lanthanum compounds have numerous applications as catalysts, additives in glass, carbon arc lamps