Molybdenum is a chemical element with the atomic number 42 in the periodic table. It occurs in an abundance of 1.5 parts per million in Earth’s crust. This refractory metal has three valence electrons and adopts the oxidation states of +2 to +6 in the compounds. Out of all naturally occurring elements, only carbon, tungsten, rhenium, osmium, and tantalum have higher melting points than molybdenum.
Chemical and Physical Properties of Molybdenum
The symbol in the periodic table of elements:
Atomic number: 42
Atomic weight (mass): 95.94 g.mol-1
Group number: 6 (Refractory metal)
Period: 5 (d-block)
Color: A silver-gray metal
Physical state: Solid at room temperature
Half-life: From 23(19) milliseconds to 1×1019 years
Electronegativity according to Pauling: 1.8
Density: 10.2 g.cm-3 at 20°C
Melting point: 2622°C, 4752°F, 2895 K
Boiling point: 4639°C, 8382°F, 4912 K
Van der Waals radius: 0.139 nm
Ionic radius: 0.068 nm (+4) ; 0.06 nm (+6)
Most characteristic isotope: 95Mo, 96Mo, 98Mo
Electronic shell: [Kr] 4d55s1
The energy of the first ionization: 651 kJ.mol -1
The energy of the second ionization: N/A
Discovery date: In 1781 by Peter Jacob Hjelm
With the periodic table symbol Mo, atomic number 42, atomic mass of 95.94 g.mol-1, and electron configuration [Kr] 4d55s1, molybdenum is a silver-gray refractory and corrosion-resistant metal. It’s very hard and tough, but also softer and more ductile than tungsten.
Molybdenum reaches its boiling point at 4639°C, 8382°F, 4912 K, while the melting point is achieved at X2622°C, 4752°F, 2895 K. This refractory metal has an electronegativity of 1.8 according to Pauling, whereas the atomic radius according to van der Waals is 0.139 nm. It’s non-reactive with oxygen or water at room temperature.
How Was Molybdenum Discovered?
Until 1778, the soft black mineral molybdenite (molybdenum sulfide, MoS2) was assumed to be a lead ore. The same year, the Swedish chemist Carl W. Scheele (1742 – 1786) attempted an experiment on a molybdenite sample in order to prove his belief that there’s a new, undiscovered element in the substance. Indeed, he succeeded in proving that the mineral molybdaina (now molybdenite) contains sulfur and a new, unknown metal. Unfortunately, he wasn’t able to isolate it.
After a series of unsuccessful trials, Sheele decided to ask his fellow colleague, the Swedish chemist Peter Jacob Hjelm for assistance. Following Sheele’s advice and directions, Hjelm finally managed to isolate the molybdenum metal, several years after Scheele detected the presence of the new element in the molybdenum sulfide sample.
First, Hjelm made a paste by mixing ground molybdic acid and carbon in linseed oil. After this step of the groundbreaking experiment, he exposed the mixture to red heat. The result was a pure metal form of the element 42.
How Did Molybdenum Get Its Name?
The name of this chemical element originates from the Greek word ‘molybdos‘, meaning ‘lead’. This term was chosen for molybdenum because, in the past, a soft and black mineral labeled as molybdenite (or molybdena) was used in the making of pencils, instead of graphite.
Since these two substances were found to be extremely similar, it was thought that the black mineral also contains lead. Today we know that it was molybdenum disulfide (MoS2).
Where Can You Find Molybdenum?
Despite being the 42nd most abundant element in the Universe, molybdenum cannot be found freely in nature in its pure, elemental form. It’s mostly obtained from the mineral molybdenite (molybdenum disulfide, MoS2), lead molybdate, PbMoO4 (wulfenite), and MgMoO4.
Typically, the concentrated mineral molybdenite is exposed to high temperatures and air in order for molybdenum trioxide (MoO3, or technical molybdic oxide) to be produced for commercial purposes. After this, the derived substance undergoes purification and is reduced with hydrogen to the metal form of molybdenum:
MoO3 + 3H2 → Mo + 3H2O
The powdery form of the molybdenum metal is produced by a hydrogen reduction of a chemically pure molybdic oxide or ammonium molybdate. Later, this powder is converted to solid metal by the process of arc-casting or by the powder-metallurgy process.
Molybdenum can also be recovered as a by-product of tungsten and copper mining. The United States, Chile, China, Peru, Mexico, and Canada are the world’s largest producers of molybdenum metal for commercial purposes. Also, the largest mining sites are located in these countries.
Molybdenum in Everyday Life
This chemical element occurs as an essential part of many enzymes, such as nitrogenase and xanthine oxidase. The enzyme nitrogenase is responsible for turning the nitrogen into compounds that support the synthesis and utilization of proteins by the human body, the plants, as well as various types of bacteria, and all higher eukaryote organisms.
Since protein metabolism is essential for all life forms, molybdenum plays a vital role in the synthesis of proteins. By being one of the essential trace elements found in the enzyme xanthine oxidase, molybdenum is directly responsible for the waste processing by the human body.
Apart from being one of the essential trace elements for animals and plants, molybdenum plays a significant role as a catalyst in the industry. Thus, this chemical element has been included as one of the most vital agents in the following processes:
- Olefin metathesis;
- Chemical oxidative processes, etc.
Molybdenum is widely applied in the production of ferrous and nonferrous alloys as an alloying agent. At high temperatures, this chemical element is used in alloys with steel and other metals in order to add strength and hardness to them while reinforcing the anti-corrosive properties of the metal alloy.
Molybdenum and Health
This micronutrient supports many metabolic functions of the human body. The most significant one of them is certainly the breakdown of proteins and amino acids. Molybdenum also helps the body to break down some toxic substances, such as alcohol by supporting the function of the molybdenum-dependent enzymes.
As a cofactor (catalyst) of the human enzymes (sulfite oxidase, xanthine oxidase, aldehyde oxidase, and mitochondrial amidoxime-reducing component) this mineral also participates in the cell energy production, processing of wastes by the body, the proper development of the nervous system, etc.
What is Molybdenum Deficiency?
Molybdenum deficiency is closely related to low dietary molybdenum levels in the blood. However, this clinical picture is relatively rare, since our body needs an extremely small amount of molybdenum.
Low amounts of molybdenum may affect the synthesis of some key enzymes. This may lead to esophageal cancer and molybdenum cofactor deficiency – a rare condition that is characterized by brain dysfunction (Encephalopathy). In addition, when the molybdenum levels in our body are insufficient, it causes a build-up of uric acid in the blood, which triggers the extremely painful condition of inflamed joints.
Our body needs a vast list of minerals in order to maintain homeostasis. Some of them need to be supplemented additionally in a form of chemical supplements. However, the molybdenum we receive from our daily intake is sufficient for the needs of our body.
This micronutrient can be found in the following foods that have a high molybdenum content:
- Legumes (peas, lentils);
- Kidney beans
- Lima beans;
- Soy products (soy milk, soybeans, and tofu);
- Dairy products (cheese, yogurt)
- Leafy vegetables;
- Whole grains;
This micronutrient is easily absorbed from the diet. However, the largest portion of it (which may amount to almost 90%) is excreted through urine. The remaining concentrations of molybdenum are stored in the liver, bones, and kidneys.
Dietary reference intakes
According to the Food and Nutrition Board, Institute of Medicine (Office of Dietary Supplements), the Adequate Intake (AI) comes in a form of recommended dietary allowances (RDA) of molybdenum, which for adults is 45 micrograms per day. Pregnant and lactating women need a slightly larger dose – about 50 micrograms. Most people’s diets provide more than the necessary 45 micrograms of molybdenum intake per day. The tolerable upper intake level (UL) for this micronutrient is 2000 micrograms per day.
In ruminants, molybdenum supplement helps prevent anemia by mobilizing the iron in the bloodstream. However, an excessive dietary intake of molybdenum may trigger a secondary copper deficiency. In turn, this may lead to anemia, iron storage disease (excess levels of iron in the blood), and Wilson’s disease.
A study on dietary reference intakes for vitamin A, vitamin K, and many other substances, conducted by R. Russell, gives an excellent insight into this matter.
Important: Please note that this molybdenum fact sheet is for educational and informative purposes only. This list is not complete and many other drugs may interact with molybdenum, including prescription and over-the-counter medicines, proton pump inhibitor (PPI) drugs, vitamins, and herbal products.
We would hereby like to strongly advise you to seek medical advice from a qualified healthcare provider or trained health professionals prior to treating any medical problems or adding manganese supplements to your diet. Please have in mind that high levels of molybdenum in the body may result in severe side effects and high toxicity.
How Dangerous Is Molybdenum?
Molybdenum and its compounds are generally considered to be very toxic substances. Strongly associated with mining or metal production, exposure to high levels of molybdenum typically occurs at the working place. It may lead to some severe diseases caused by molybdenum toxicity, such as liver dysfunction with hyperbilirubinemia, or gout.
What Are the Symptoms of Molybdenum Toxicity?
The individuals who have been exposed to high levels of molybdenum may experience some of the following symptoms:
- Erythema (redness of the skin);
- Articular deformities;
- Weight loss;
- Joint pain in the feet, hands, and knees;
- Edema (swelling) of the joint areas of the body.
Environmental Effects of Molybdenum
Being an essential trace element for all life forms, molybdenum can lead to fatal consequences if the levels of this micronutrient are too low, and vice versa – the dangerous molybdenum toxicity may occur if the accumulated levels of this chemical element are too high.
Isotopes of Molybdenum
Element 42 has 33 isotopes. Seven of them occur naturally. Those are the molybdenum forms with the atomic numbers 92, 94, 95, 96, 97, 98, and 100. Molybdenum-96 is the most common stable form of this chemical element. It occurs in 24.14% of all molybdenum found on our planet.
The natural form of molybdenum is made by seven stable isotopes:
- Molybdenum-92 (15.84 percent);
- Molybdenum-94 (9.04 percent);
- Molybdenum-95 (15.72 percent);
- Molybdenum-96 (16.53 percent);
- Molybdenum-97 (9.46 percent);
- Molybdenum-98 (23.78 percent);
- Molybdenum-100 (9.13 percent).
Among these naturally occurring forms of molybdenum, only the molybdenum-100 is an unstable isotope. While speaking of unstable atomic shells, it’s worth noting that all unstable isotopes of molybdenum decay into isotopes of technetium, zirconium, niobium, and ruthenium. The decaying processes of each isotope of molybdenum are presented in the following table:
|Z||N||Isotopic mass (Da)
[n 2][n 3]
[n 7][n 8]
|Natural abundance (mole fraction)|
|Excitation energy||Normal proportion||Range of variation|
|87Mo||42||45||86.92733(24)||14.05(23) s||β+ (85%)||87Nb||7/2+#|
|β+, p (15%)||86Zr|
|92Mo||42||50||91.906811(4)||Observationally Stable[n 9]||0+||0.14649(106)|
|98Mo[n 10]||42||56||97.90540482(21)||Observationally Stable[n 11]||0+||0.24292(80)|
|99Mo[n 10][n 12]||42||57||98.9077119(21)||2.7489(6) d||β−||99mTc||1/2+|
|100Mo[n 13][n 10]||42||58||99.907477(6)||8.5(5)×1018 a||β−β−||100Ru||0+||0.09744(65)|
|110Mo||42||68||109.92973(43)#||0.27(1) s||β− (>99.9%)||110Tc||0+|
|β−, n (<.1%)||109Tc|
List of Molybdenum Compounds
Molybdenum typically adopts the oxidation states of +2 to +6. At high temperatures, this chemical element forms direct reactions with nitrogen, boron, silicon, and carbon. The compounds made by the aforementioned elements with molybdenum are hard, refractory, and chemically inert.
Relatively unreactive with acids, molybdenum is rapidly attacked by potassium nitrate, sodium hydroxide, or sodium peroxide. When exposed to red heat, this element readily reacts with oxygen in order to produce trioxides. Otherwise, it is rather inter to O2 at a temperature of around 20°C. The chemical reaction of molybdenum with fluorine at room temperature produces hexafluorides.
The following is a list of minerals that present a rich source of molybdenum:
Common Compounds of Molybdenum
The most common reactions of molybdenum with the other elements can be found in the following list:
- Ammonium Tetrathiomolybdate
- Molybdenum(II) Sulfate
- Molybdenum(IV) Carbonate
- Molybdenum(IV) Phosphate
- Molybdenum(V) Oxide
- Molybdenum(II) Nitrate
- Molybdenum(VI) Hydrogen Phosphate
- Molybdenum Trioxide
- Molybdenum(II) Chloride
- Molybdenum(III) Nitride
- Molybdenum Dichromate
- Molybdenum Disulfide
- Molybdenum(III) Chloride
- Molybdenum(VI) Sulfate
- Molybdenum(III) Permanganate
- Molybdenum(III) Bromide
- Molybdenum(V) Chloride
- Molybdenum(II) Bromide
- Molybdenum(VI) Benzoate
- Molybdenum(IV) Oxide
- Molybdenum Sulfite
- Molybdenum(II) Fluoride
- Molybdenum(V) Bromide
- Molybdenum(III) Sulfide
- Molybdenum(VI) Hexafluoride
- Molybdenum Hexacarbonyl
- Molybdenum(VI) Chromate
- Molybdenum(III) Iodide
- Molybdenum(V) Sulfide
- Molybdenum(V) Selenate
- Molybdenum(VI) Pyrophosphate
- Molybdenum(II) Hydrogen Sulfate
5 Interesting Facts and Explanations
- Molybdenum is the 42nd most abundant element in the Universe, and 54th most abundant chemical element in the Earth’s crust.
- Not only molybdenum is almost as abundant as the element tungsten, but it also resembles the chemical and physical properties of this element.
- Ferromolybdenum is an alloy containing at least 60 percent of molybdenum. It’s produced by the ignition of a mixture made by technical oxide and iron oxide.
- Our body needs only a third of a gram of molybdenum for the entire lifetime!
- A refractory metal is a metal that characterizes with very high resistance to heat and wear.