Period 6 element between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods). Lanthanum is a chemical element with the symbol La and atomic number 57. It is the first element in the lanthanide series. It is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series,
Sterling silver Netherlands, the Baltic, Germany, and even deeper regions of central Europe." The sterling alloy originated in continental Europe and was being used for commerce as early as the 12th century in the area that is now northern Germany. In England the composition of sterling silver was subject to official assay at some date before 1158, during the reign of Henry II, but its purity was probably regulated from centuries earlier, in Saxon times. A piece of sterling silver dating from Henry II's reign was used as a standard in the Trial of the Pyx until it was deposited at the