Molybdenum (Greek: mólybdos = lead) is a chemical element symbol Mo and the atomic number 42; it is a transition metal. As a trace element, molybdenum plays an important role in the nitrogen supply for plants since it binds atmospheric nitrogen. In the event of molybdenum deficiency, nitrogen degradation does not work properly and the number of amino acids decreases. Molybdenum is mainly made from molybdenite or molybdenum sulfide and was mistaken for galena and graphite for a long time. Pure molybdenum is plastically ductile, but even the smallest contamination with oxygen or nitrogen makes it very brittle. This made processing much more difficult, which is why molybdenum did not attract attention for a long time.