Molybdenum

Molybdenum is a silvery transition metal with symbol Mo and atomic number 42. Its high melting point and ability to strengthen alloys make it valuable in steelmaking and high-temperature applications.

Transition metal: An element whose atoms or ions have partially filled d orbitals. Molybdenum’s d-electron chemistry places it among the transition metals.
Chemical element: A pure substance defined by atoms with the same number of protons. Molybdenum is defined by its 42 protons, regardless of isotope or chemical compound.
Carl Wilhelm Scheele: A Swedish chemist whose investigations identified several elements and compounds in the eighteenth century. Scheele showed that molybdenite contained an unknown element, distinguishing it from graphite.
Stainless steel: Iron-based steel containing enough chromium to resist rust and corrosion. Molybdenum-containing grades enable equipment to withstand corrosive chemical and marine environments.
Molybdenum carbide: A hard compound of molybdenum and carbon used in wear-resistant materials and catalysis. Carbon forms hard, refractory compounds with molybdenum for specialized applications.
Atomic number: The number of protons in an atom’s nucleus, which determines its chemical element. The value 42 distinguishes molybdenum from every other element.
Peter Jacob Hjelm: A Swedish chemist who isolated metallic molybdenum in 1781. Hjelm’s reduction of molybdenum oxide produced the first metal sample.
Molybdenum cofactor deficiency: A rare inherited disorder in which impaired cofactor synthesis disrupts several molybdenum-dependent enzymes. The disorder shows the severe consequences of failing to activate molybdenum in human metabolism.
Molybdenum oxide: A family of molybdenum-oxygen compounds, including molybdenum trioxide, used in catalysts and materials. Molybdenum changes oxidation state readily, producing oxides with distinct chemical uses.
Molybdenum-99: A radioactive molybdenum isotope that decays to technetium-99m, widely used in medical imaging. This isotope links molybdenum production to diagnostic nuclear medicine.

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