Properties and Overview of Molybdenum

Overview:

Molybdenum (Mo) with the chemical symbol Mo and atomic number 42, is a transition metal known for its high strength, durability, and corrosion resistance. It was discovered in 1778 by the Swedish chemist Carl Wilhelm Scheele, who identified it as a distinct element from lead. Molybdenum is found in the Earth's crust but is not as abundant as other metals. It typically occurs in minerals such as molybdenite (MoS₂), from which it is primarily extracted. Physically, molybdenum is a silvery-gray metal with a very high melting point of 2,623°C, making it one of the highest melting points of any element. Its boiling point is even higher at 4,639°C. Molybdenum has a density of 10.28g/cm³, placing it in the range of moderately dense metals. It is known for its hardness and strength, particularly at high temperatures, which makes it an essential material in applications requiring durability under extreme conditions.
Chemically, molybdenum exhibits several oxidation states, the most common being +4 and +6. The element forms various compounds, including oxides, sulfides, and halides. Molybdenum trioxide (MoO₃) is one of its most important compounds, used in various chemical processes. Molybdenum is relatively stable in air at room temperature but can form a thin oxide layer on its surface, which helps protect it from further corrosion. It is resistant to most acids but can be attacked by strong oxidizing acids like nitric acid. Molybdenum's chemical reactivity is moderate, and it can form complex compounds with other elements, particularly in the presence of oxygen or sulfur.
In terms of safety, molybdenum is generally considered to have low toxicity. It is an essential trace element for plants and animals, necessary for various biological functions, including the enzymatic processes involved in nitrogen fixation in plants and the metabolism of sulfur-containing amino acids in animals. However, excessive exposure to molybdenum, particularly in industrial settings, can lead to health issues. Occupational exposure to molybdenum dust or fumes can cause respiratory problems and, in extreme cases, lung fibrosis. Chronic overexposure to molybdenum can also lead to a condition known as molybdenosis, particularly in livestock, where high levels of molybdenum interfere with copper metabolism, leading to copper deficiency. The risk of molybdenum toxicity in humans is generally low, but proper industrial hygiene and safety measures should be observed to minimize exposure.

Production:

The production of molybdenum primarily involves mining its chief ore, molybdenite. The ore is concentrated through froth flotation, which separates the molybdenum-containing mineral from other minerals. The concentrated molybdenite is then roasted in air to convert it into molybdenum trioxide (MoO₃). This oxide can be further processed by hydrogen reduction to produce pure molybdenum metal. Major molybdenum producers include China, the United States, and Chile, with large deposits also found in Canada and Peru.

Applications:

Molybdenum has many applications thanks to its high melting point, strength, and corrosion resistance. Steel is used as an alloying element to enhance the strength, toughness, and resistance to wear and corrosion of steel and cast iron. Molybdenum is crucial in producing high-strength steel alloys used in pipelines, tools, military hardware, and engine parts. In the chemical industry, molybdenum compounds serve as catalysts in various chemical reactions, including refining petroleum and producing acrylic acid. Molybdenum disulfide (MoS₂) is used as a lubricant, particularly in situations where oils are ineffective due to high temperatures or pressures. Additionally, molybdenum is vital in the electronics and aerospace industries, where its properties are leveraged in high-temperature environments and advanced materials.

Summary:

Molybdenum is a versatile transition metal known for its high melting point, strength, and corrosion resistance. It is used extensively in the steel industry to produce high-strength alloys and as a catalyst in the chemical industry. Molybdenum's physical and chemical properties make it suitable for applications in high-temperature environments and advanced technologies. While it is essential for biological processes in trace amounts, excessive exposure can pose health risks, emphasizing the importance of safety measures in industrial contexts.

See a comprehensive list of atomic, electrical, mechanical, physical and thermal properties for molybdenum below: