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About Molybdenum

Molybdenum Bohr

The chemical and physical properties of molybdenum metal and its alloys are prized by a wide range of industries ranging from defense, avionics, metallurgy, glassmaking, pigments and dyes, organometallic chemistry, and the manufacturing of photovoltaics and semiconductor devices. A silvery gray transition metal, molybdenum is also one of the refractory metals, a group of metals with the shared properties of extremely high melting points and thermal conductivity, low thermal expansion and vapor pressure, excellent dimensional stability and creep resistance, and resistance to oxidation; its chemical behavior is similar to that of tungsten. Molybdenum has the sixth highest melting point of all elements and one of the lowest coefficients of thermal expansion among commercial metals, yet possesses a density only 25% higher than iron. It is the 54th most abundant element in the earth’s crust but does not occur freely in nature, rather present in oxide forms with various valence states. Common molybdenum-containing minerals include molybdenite (molybdenum sulfide), wulfenite (lead molybdate), and powellite; the metal is commercially produced via the direct mining of molybdenite as well as the production of tungsten and copper.

Molybdenum-containing minerals have been known since ancient times, but the element was often identified as lead; its current name is derived from the Ancient Greek word for lead, molybdos, owing to the confusion between lead sulfide and molybdenum sulfides, the latter of which was originally referred to as molybdena. Carl Wilhelm Scheele identified the element in 1778 by producing molybdenum oxide from molybdenite (naming it “terra molybdaenae”); in 1781, Peter Jacob Hjelm heated linseed oil and carbon combined with molybdic acid to yield the metal.

Molybdenum is toxic in high amounts but plays a critical biological role as a cofactor required for enyzme function; it did not play a significant commercial role until utilized in German artillery during World War II. Since then, its role as an alloying agent has composed more than 75% of its usage; often referred to as “moly,” it lends numerous advantages including increased hardness, strength, creep resistance, resistance to wear and corrosion, weldability, and stability in high stress, high temperature environments. Besides quenched and tempered steels, prevalent molybdenum alloys used in x-ray tubes, forging tools, and other applications include Hastelloys, ferromolybdenum, Titanium-Zirconium-Molybdenum (TZM), and Molybdenum-Lanthanum (lanthanated moly, or MoLa) which exhibits higher strength and dimensional stability than TZM. Commercial products that benefit from the use of molybdenum include armor, aircraft engine components, glass melting electrodes, valves, boiler plates, ribbons and wires for lighting, semiconductor base plates, hot-zones and heat sinks, sputtering targets for photovoltaic cell coatings and flat screens, crucibles for sapphire growth, circuit inks, and microwave devices. The isotope Molybdenum-99 is also used in nuclear imaging.

Molybdenum compounds are often used as industrial catalysts for removal of sulfide compounds from crude oil, converting water to hydrogen gas, producing formaldehyde and acrylonitrile, and, in the case of the n-type semiconductor molybdenum trioxide, acting as a photocatalyst; other applications include lubricants and pigments. Molybdenum disulfide and molybdensum diselenide have the ability to form two-dimensional thin films analagous to those of carbon (in the form of graphene) for use in flexible electronics; electrodes composed of MoS2-graphene nanosheet composites vastly improve performance of next-generation sodium air batteries.

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Molybdenum is used in high-pressure and high-temperature environments as pigments and catalysts. It is also found used in nuclear reactors, aerospace components, and some forms of steel alloys to add hardness and raise melting points. High Purity (99.999%) Molybdenum Oxide (MoO3) Powder Molybdenum is available as metal and compounds with purities from 99% to 99.999% (ACS grade to ultra-high purity). High Purity (99.999%) Molybdenum (Mo) Sputtering Target Elemental or metallic forms include pellets, rod, wire and granules for evaporation source material purposes. Molybdenum nanoparticles and nanopowders are also available. Molybedenum oxides are available in powder and dense pellet form for such uses as optical coating and thin film applications.Oxides tend to be insoluble. Molybdenum fluorides are other insoluble forms for uses in which oxygen is undesirable such as metallurgy, chemical and physical vapor deposition and in some optical coatings. Molybdenum is also available in soluble forms including chlorides, nitrates and acetates. These compounds can be manufactured as solutions at specified stoichiometries.

Molybdenum Properties

Molybdenum (Mo) atomic and molecular weight, atomic number and elemental symbolMolybdenum is a Block D, Group 6, Period 5 element. Molybdenum Bohr ModelThe number of electrons in each of molybdenum's shells is 2, 8, 18, 13, 1 and its electronic configuration is [Kr] 4d5 5s1. The molybdenum atom has a radius of and its Van der Waals radius is In its elemental form, CAS 7439-98-7, molybdenum has a gray metallic appearance. Elemental MolybdenumMolybdenum is the 54th most abundant element in the earth's crust. It has the third highest melting point of any element, exceeded only by tungsten and tantalum. Molybdenum does not occur naturally as a free metal, it is found in various oxidation states in minerals. The primary commercial source of molybdenum is molybdenite, although it is also recovered as a byproduct of copper and tungsten mining. Molybdenum was first discovered by Carl Wilhelm in 1778. The origin of the name molybdenum comes from the Greek word molubdos meaning lead.

Symbol: Mo
Atomic Number: 42
Atomic Weight: 95.96
Element Category: transition metal
Group, Period, Block: 6, 5, d
Color: gray metallic/ gray-white
Other Names: Molybdéne, Molibdeno
Melting Point: 2622°C, 4751.6°F, 2895.15 K
Boiling Point: 4639°C, 8382.2°F, 4912.15 K
Density: 10.28 g·cm3
Liquid Density @ Melting Point: 9.33 g·cm3
Density @ 20°C: 10.2 g/cm3
Density of Solid: 10280 kg·m3
Specific Heat: 0.25 (kJ/kg K)
Superconductivity Temperature: 0.915 [or -272.235 °C (-458.02 °F)] K
Triple Point: N/A
Critical Point: N/A
Heat of Fusion (kJ·mol-1): 27.6
Heat of Vaporization (kJ·mol-1): 589.9
Heat of Atomization (kJ·mol-1): 656.55
Thermal Conductivity: 138 W·m-1·K-1
Thermal Expansion: (25 °C) 4.8 µm·m-1·K-1
Electrical Resistivity: (20 °C) 53.4 nΩ·m
Tensile Strength: N/A
Molar Heat Capacity: 24.06 J·mol-1·K-1
Young's Modulus: 329 GPa
Shear Modulus: 126 GPa
Bulk Modulus: 230 GPa
Poisson Ratio: 0.31
Mohs Hardness: 5.5
Vickers Hardness: 1530 MPa
Brinell Hardness: 1500 MPa
Speed of Sound: (r.t.) 5400 m·s-1
Pauling Electronegativity: 2.16
Sanderson Electronegativity: 1.15
Allred Rochow Electronegativity: 1.3
Mulliken-Jaffe Electronegativity: N/A
Allen Electronegativity: N/A
Pauling Electropositivity: 1.84
Reflectivity (%): 58
Refractive Index: N/A
Electrons: 42
Protons: 42
Neutrons: 54
Electron Configuration: [Kr] 4d5 5s1
Atomic Radius: 139 pm
Atomic Radius,
non-bonded (Å):
Covalent Radius: 154±5 pm
Covalent Radius (Å): 1.46
Van der Waals Radius: 200 pm
Oxidation States: 6, 5, 4, 3, 2, 1, -1, -2 (strongly acidic oxide)
Phase: Solid
Crystal Structure: body-centered cubic
Magnetic Ordering: paramagnetic
Electron Affinity (kJ·mol-1) 72.146
1st Ionization Energy: 684.32 kJ·mol-1
2nd Ionization Energy: 1559.21 kJ·mol-1
3rd Ionization Energy: 2617.67 kJ·mol-1
CAS Number: 7439-98-7
EC Number: 231-107-2
MDL Number: MFCD00003465
Beilstein Number: N/A
SMILES Identifier: [Mo]
InChI Identifier: InChI=1S/Mo
PubChem CID: 23932
ChemSpider ID: 22374
Earth - Total: 2.35 ppm
Mercury - Total: 1.81 ppm
Venus - Total: 2.47 ppm
Earth - Seawater (Oceans), ppb by weight: 10
Earth - Seawater (Oceans), ppb by atoms: 0.64
Earth -  Crust (Crustal Rocks), ppb by weight: 1100
Earth -  Crust (Crustal Rocks), ppb by atoms: 230
Sun - Total, ppb by weight: 9
Sun - Total, ppb by atoms: 0.1
Stream, ppb by weight: 0.8
Stream, ppb by atoms: 0.008
Meterorite (Carbonaceous), ppb by weight: 1200
Meterorite (Carbonaceous), ppb by atoms: 250
Typical Human Body, ppb by weight: 100
Typical Human Body, ppb by atom: 7
Universe, ppb by weight: 5
Universe, ppb by atom: 0.1
Discovered By: Carl Wilhelm Scheele
Discovery Date: 1778
First Isolation: Peter Jacob Hjelm (1781)

Health, Safety & Transportation Information for Molybdenum

Molybdenum is toxic unless it is in small quantities. Safety data for Molybdenum and its compounds can vary widely depending on the form. For potential hazard information, toxicity, and road, sea and air transportation limitations, such as DOT Hazard Class, DOT Number, EU Number, NFPA Health rating and RTECS Class, please see the specific material or compound referenced in the Products tab. The below information applies to elemental (metallic) Molybdenum.

Safety Data
Signal Word Danger
Hazard Statements H228
Hazard Codes F
Risk Codes 11
Safety Precautions 9-16-36/37/39
RTECS Number QA4680000
Transport Information UN 3089 4.1/PG 2
WGK Germany nwg
Globally Harmonized System of
Classification and Labelling (GHS)
Review and Print SDS for Molybdenum Metal


Date Created: 05/15/2015
Date Revised: 05/15/2015


Product Name: Molybdenum Metal

Product Number: All applicable American Elements product codes, e.g. MO-M-02, MO-M-03, MO-M-04, MO-M-05

CAS #: 7439-98-7

Relevant identified uses of the substance: Scientific research and development

Supplier details:
American Elements
1093 Broxton Ave. Suite 2000
Los Angeles, CA 90024
Tel: +1 310-208-0551
Fax: +1 310-208-0351

Emergency telephone number:
Domestic, North America +1 800-424-9300
International +1 703-527-3887


Classification of the substance or mixture
Classification according to Regulation (EC) No 1272/2008
The substance is not classified as hazardous to health or the environment according to the CLP regulation.
Classification according to Directive 67/548/EEC or Directive 1999/45/EC
Not applicable
Information concerning particular hazards for human and environment:
No information known.
Hazards not otherwise classified
No information known.
Label elements
Labelling according to Regulation (EC) No 1272/2008
Not applicable
Hazard pictograms
Not applicable
Signal word
Not applicable
Hazard statements
Not applicable
WHMIS classification
Not controlled
Classification system
HMIS ratings (scale 0-4)
(Hazardous Materials Identification System)

Health (acute effects) = 0
Flammability = 0
Physical Hazard = 0
Other hazards
Results of PBT and vPvB assessment
PBT: Not applicable.
vPvB: Not applicable.


Chemical characterization: Substances
CAS# Description:
7439-98-7 Molybdenum
Identification number(s):
EC number: 231-107-2


Description of first aid measures
General information
No special measures required.
After inhalation
Seek medical treatment in case of complaints.
After skin contact
Generally the product does not irritate the skin.
After eye contact
Rinse opened eye for several minutes under running water. If symptoms persist, consult a doctor.
After swallowing
If symptoms persist consult doctor.
Information for doctor
Most important symptoms and effects, both acute and delayed
No further relevant information available.
Indication of any immediate medical attention and special treatment needed
No further relevant information available.


Extinguishing media
Suitable extinguishing agents
Special powder for metal fires. Do not use water.
For safety reasons unsuitable extinguishing agents
Special hazards arising from the substance or mixture
If this product is involved in a fire, the following can be released:
Molybdenum oxides
Advice for firefighters
Protective equipment:
No special measures required.


Personal precautions, protective equipment and emergency procedures
Not required.
Environmental precautions:
Do not allow product to reach sewage system or any water course.
Do not allow to penetrate the ground/soil.
Methods and material for containment and cleaning up:
Pick up mechanically.
Prevention of secondary hazards:
No special measures required.
Reference to other sections
See Section 7 for information on safe handling
See Section 8 for information on personal protection equipment.
See Section 13 for disposal information.


Precautions for safe handling
Keep container tightly sealed.
Store in cool, dry place in tightly closed containers.
Information about protection against explosions and fires:
No special measures required.
Conditions for safe storage, including any incompatibilities
Requirements to be met by storerooms and receptacles:
No special requirements.
Information about storage in one common storage facility:
Do not store together with acids.
Store away from oxidizing agents.
Further information about storage conditions:
Keep container tightly sealed.
Store in cool, dry conditions in well sealed containers.
Specific end use(s)
No further relevant information available.


Additional information about design of technical systems:
No further data; see section 7.
Control parameters
Components with limit values that require monitoring at the workplace: 7439-98-7 Molybdenum (100.0%)
PEL (USA) Long-term value: 5* 15** mg/m³ as Mo;*soluble compds., **insol.compds.:total dust
TLV (USA) Long-term value: 10* 3** mg/m³ as Mo; *inhalable fraction ** respirable fraction
EL (Canada) Long-term value: 3* 10** mg/m³ as Mo; *respirable **inhalable
EV (Canada) Long-term value: 10* 3** 0.5*** mg/m³ metal,insol.compd.:*inh;**resp;sol.compd.:***resp
Additional information: No data
Exposure controls
Personal protective equipment
General protective and hygienic measures
The usual precautionary measures for handling chemicals should be followed.
Maintain an ergonomically appropriate working environment.
Breathing equipment: Not required.
Recommended filter device for short term use:
Use a respirator with type N95 (USA) or PE (EN 143) cartridges as a backup to engineering controls. Risk assessment should be performed to determine if air-purifying respirators are appropriate. Only use equipment tested and approved under appropriate government standards.
Protection of hands: Not required.
Material of gloves
Nitrile rubber, NBR
Penetration time of glove material (in minutes) 480
Glove thickness 0.11 mm
Eye protection: Safety glasses
Body protection: Protective work clothing.


Information on basic physical and chemical properties
General Information
Form: Solid in various forms
Color: Dark grey
Odor: Not determined
Odor threshold: Not determined.
pH-value: Not applicable.
Change in condition
Melting point/Melting range: 2623 °C (4753 °F)
Boiling point/Boiling range: 4639 °C (8382 °F)
Sublimation temperature / start: Not determined
Flammability (solid, gaseous): Not determined.
Ignition temperature: Not determined
Decomposition temperature: Not determined
Auto igniting: Not determined.
Danger of explosion: Not determined.
Explosion limits:
Lower: Not determined
Upper: Not determined
Vapor pressure: Not applicable.
Density at 20 °C (68 °F): 10.22 g/cm³ (85.286 lbs/gal)
Relative density: Not determined.
Vapor density: Not applicable.
Evaporation rate: Not applicable.
Solubility in / Miscibility with Water: Not determined
Partition coefficient (n-octanol/water): Not determined.
dynamic: Not applicable.
kinematic: Not applicable
Other information
No further relevant information available.


No information known.
Chemical stability
Stable under recommended storage conditions.
Thermal decomposition / conditions to be avoided:
Decomposition will not occur if used and stored according to specifications.
Possibility of hazardous reactions
Reacts with strong oxidizing agents
Conditions to avoid
No further relevant information available.
Incompatible materials:
Oxidizing agents
Hazardous decomposition products:
Molybdenum oxides


Information on toxicological effects
Acute toxicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains acute toxicity data for this substance.
LD/LC50 values that are relevant for classification: No data
Skin irritation or corrosion: May cause irritation
Eye irritation or corrosion: May cause irritation
Sensitization: No sensitizing effects known.
Germ cell mutagenicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains mutation data for this substance.
No classification data on carcinogenic properties of this material is available from the EPA, IARC, NTP, OSHA or ACGIH.
Reproductive toxicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains reproductive data for this substance.
Specific target organ system toxicity - repeated exposure: No effects known.
Specific target organ system toxicity - single exposure: No effects known.
Aspiration hazard: No effects known.
Subacute to chronic toxicity:
The Registry of Toxic Effects of Chemical Substances (RTECS) contains multiple dose toxicity data for this substance.
Additional toxicological information:
To the best of our knowledge the acute and chronic toxicity of this substance is not fully known.
Carcinogenic categories
OSHA-Ca (Occupational Safety & Health Administration)
Substance is not listed.


Aquatic toxicity:
No further relevant information available.
Persistence and degradability
No further relevant information available.
Bioaccumulative potential
No further relevant information available.
Mobility in soil
No further relevant information available.
Additional ecological information:
General notes:
Do not allow undiluted product or large quantities to reach ground water, water course or sewage system.
Avoid transfer into the environment.
Results of PBT and vPvB assessment
PBT: Not applicable.
vPvB: Not applicable.
Other adverse effects
No further relevant information available


Waste treatment methods
Consult state, local or national regulations to ensure proper disposal.
Uncleaned packagings:
Disposal must be made according to official regulations.


Not applicable
UN proper shipping name
Not applicable
Transport hazard class(es)
Not applicable
Packing group
Not applicable
Environmental hazards:
Not applicable.
Special precautions for user
Not applicable.
Transport in bulk according to Annex II of MARPOL73/78 and the IBC Code
Not applicable.
Transport/Additional information:
Marine Pollutant (DOT):
UN "Model Regulation":


Safety, health and environmental regulations/legislation specific for the substance or mixture
National regulations
All components of this product are listed in the U.S. Environmental Protection Agency Toxic Substances Control Act Chemical substance Inventory.
All components of this product are listed on the Canadian Domestic Substances List (DSL).
SARA Section 313 (specific toxic chemical listings)
Substance is not listed.
California Proposition 65
Prop 65 - Chemicals known to cause cancer
Substance is not listed.
Prop 65 - Developmental toxicity
Substance is not listed.
Prop 65 - Developmental toxicity, female
Substance is not listed.
Prop 65 - Developmental toxicity, male
Substance is not listed.
Information about limitation of use:
For use only by technically qualified individuals.
Other regulations, limitations and prohibitive regulations
Substance of Very High Concern (SVHC) according to the REACH Regulations (EC) No. 1907/2006.
Substance is not listed.
The conditions of restrictions according to Article 67 and Annex XVII of the Regulation (EC) No 1907/2006 (REACH) for the manufacturing, placing on the market and use must be observed.
Substance is not listed.
Annex XIV of the REACH Regulations (requiring Authorisation for use)
Substance is not listed.
REACH - Pre-registered substances
Substance is listed.
Chemical safety assessment:
A Chemical Safety Assessment has not been carried out.


Safety Data Sheet according to Regulation (EC) No. 1907/2006 (REACH). The above information is believed to be correct but does not purport to be all inclusive and shall be used only as a guide. The information in this document is based on the present state of our knowledge and is applicable to the product with regard to appropriate safety precautions. It does not represent any guarantee of the properties of the product. American Elements shall not be held liable for any damage resulting from handling or from contact with the above product. See reverse side of invoice or packing slip for additional terms and conditions of sale. COPYRIGHT 1997-2016 AMERICAN ELEMENTS. LICENSED GRANTED TO MAKE UNLIMITED PAPER COPIES FOR INTERNAL USE ONLY.

Molybdenum Isotopes

Molybdenum has 5 stable isotopes:

Nuclide Isotopic Mass Half-Life Mode of Decay Nuclear Spin Magnetic Moment Binding Energy (MeV) Natural Abundance
(% by atom)
83Mo 82.94874(54)# 23(19) ms [6(+30-3) ms] ß+ to 83Nb; ß+ + p to 82Zr 3/2-# N/A 671.85 -
84Mo 83.94009(43)# 3.8(9) ms [3.7(+10-8) s] ß+ to 84Nb 0+ N/A 687.38 -
85Mo 84.93655(30)# 3.2(2) s ß+ to 85Nb (1/2-)# N/A 699.19 -
86Mo 85.93070(47) 19.6(11) s ß+ to 86Nb 0+ N/A 712.86 -
87Mo 86.92733(24) 14.05(23) s ß+ to 87Nb; ß+ + p to 86Zr 7/2+# N/A 723.73 -
88Mo 87.921953(22) 8.0(2) min ß+ to 88Nb 0+ N/A 737.4 -
89Mo 88.919480(17) 2.11(10) min ß+ to 89Nb (9/2+) N/A 747.34 -
90Mo 89.913937(7) 5.56(9) h EC to 90Nb 0+ N/A 761.01 -
91Mo 90.911750(12) 15.49(1) min EC to 91Nb 9/2+ N/A 770.95 -
92Mo 91.906811(4) Observationally Stable - 0+ N/A 783.69 14.84
93Mo 92.906813(4) 4.0(8)E+3 y EC to 93Nb 5/2+ N/A 791.77 -
94Mo 93.9050883(21) STABLE - 0+ N/A 800.78 9.25
95Mo 94.9058421(21) STABLE - 5/2+ -0.9142 808.86 15.92
96Mo 95.9046795(21) STABLE - 0+ N/A 817.87 16.68
97Mo 96.9060215(21) STABLE - 5/2+ -0.9335 824.08 9.55
98Mo 97.9054082(21) Observationally Stable - 0+ N/A 833.09 24.13
99Mo 98.9077119(21) 2.7489(6) d ß- to 99Tc 1/2+ 0.375 839.31 -
100Mo 99.907477(6) 8.5(5)E+18 y - to 100Ru 0+ N/A 847.39 9.63
101Mo 100.910347(6) 14.61(3) min ß- to 101Tc 1/2+ N/A 852.67 -
102Mo 101.910297(22) 11.3(2) min ß- to 102Tc 0+ N/A 860.75 -
103Mo 102.91321(7) 67.5(15) s ß- to 103Tc (3/2+) N/A 868.83 -
104Mo 103.91376(6) 60(2) s ß- to 104Tc 0+ N/A 876.91 -
105Mo 104.91697(8) 35.6(16) s ß- to 105Tc (5/2-) N/A 884.98 -
106Mo 105.918137(19) 8.73(12) s ß- to 106Tc 0+ N/A 893.06 -
107Mo 106.92169(17) 3.5(5) s ß- to 107Tc (7/2-) N/A 891.83 -
108Mo 107.92345(21)# 1.09(2) s ß- to 108Tc 0+ N/A 899.9 -
109Mo 108.92781(32)# 0.53(6) s ß- to 109Tc (7/2-)# N/A 907.98 -
110Mo 109.92973(43)# 0.27(1) s ß- to 110Tc; ß- + n to 109Tc 0+ N/A 916.06 -
111Mo 110.93441(43)# 200# ms [>300 ns] ß- to 111Tc N/A N/A 914.82 -
112Mo 111.93684(64)# 150# ms [>300 ns] ß- to 112Tc 0+ N/A 922.9 -
113Mo 112.94188(64)# 100# ms [>300 ns] ß- to 113Tc N/A N/A 921.67 -
114Mo 113.94492(75)# 80# ms [>300 ns] Unknown 0+ N/A 929.74 -
115Mo 114.95029(86)# 60# ms [>300 ns] Unknown N/A N/A 928.51 -