Technetium is a radioactive element discovered in 1937 by C. Perrier and E. G. Segré in Palermo, Italy, during the study of the by-products of deuteron bombardment of metallic molybdenum. On the basis of powder diffraction patterns carried out by Mooney on material supplied by Parker, it was later shown that technetium fits into the Periodic Table between manganese and rhenium because of its similarity in crystal structure type.