Molybdenum, element number 42 of the periodic table, lies in the table's second transition series, in Group 6A between chromium and tungsten.
It has one of the highest melting temperatures of all the elements, yet unlike most other high-melting point metals, its density is only 25% greater than iron's. Its coefficient of thermal expansion is the lowest of the engineering materials, while its thermal conductivity exceeds all but a handful of elements.