Molybdenum, with the chemical symbol Mo and an atomic number of 6, is not a naturally occurring element. It exists on earth in different mineral oxidation states. There are 35 different known isotopes that occur. It is considered a transition metal. It has low water solubility, and is actually an essential element for life in most higher organisms, including plants and human beings. Molybdenum has an exceptionally high melting point. In fact, it is the 6th highest melting point of all the elements. This property is what makes it valuable for its most common use, making metal alloys, particularly steel alloys. About 80% of molybdenum generation goes to steel production. It is also used in situations where a material is needed to withstand high pressures or temperatures, such as an ingredient in pigment. In addition, enzymes containing this element are able to catalyze the process with which to fix atmospheric nitrogen.