Molybdenum

Molybdenum: Occurrence, Properties, Uses, and Isotopes of Molybdenum

Introduction

  • Molybdenum is a transition metal present in group number VI B of the periodic table.
  • Its atomic number is 42 whereas its atomic mass is 95.95.
  • It has 42 electrons.
  • Molybdenum has 42 protons and 56 neutrons in its nucleus.
  • It is represented by the symbol “Mo”.
Naming and History

The word Molybdenum is derived from the Greek word “Molybdos” which means lead.

Molybdenite, likewise called molybdena was commonly confused for graphite and it was believed to include lead.

  • Carl W. Scheele

In 1778 Swedish scientist Carl W. Scheele verified that molybdenite was not graphite neither did it have lead.

Scheele concluded that the mineral included a new element, but he did not isolate it, as he did not have an appropriate furnace to reduce the white solid to the metal.

  • Peter J. Hjelm

In 1781, Scheele’s good friend and compatriot, Peter J. Hjelm separated the metal by reducing the white solid with carbon. He ground the two substances together making use of linseed oil to create a paste.

The paste ensured intimate contact between the carbon and molybdenite. Hjelm heated the combination highly in a shut crucible to produce the new metallic element. Hjelm called his new metal molybdenum.

Occurrence of Molybdenum

Occurrence-of-Molybden

Molybdenum does not occur freely in nature. It is present in ores and minerals. Today, the majority of molybdenum is acquired from molybdenite, wulfenite (PbMoO4), and powellite (CaMoO4).

These ores typically occur along with ores of tin and tungsten. Molybdenum is also obtained as a by-product of the mining of tungsten and copper. The major mining areas are Chile, Canada, and Russia.

Properties of Molybdenum

Molybdenum is silvery-white, hard transition metal, but is softer than tungsten. It has a high elastic modulus. It does not react with oxygen or water at room temperature and also it also withstands corrosion at standard temperature.

Of the readily available metals, only tungsten and tantalum have higher melting points. The melting point of molybdenum is 2623 ° C and its boiling point is 4639 ° C. It has a density of 10.2 grams per cubic centimeter and exists as solid at room temperature.

Molybdenum in Biological System

Molybdenum is a toxic element but trace amounts of it are required for living organisms. It is necessary for the proper functioning of enzymes. Almost 50 enzymes in plants and animals need molybdenum.

The enzyme nitrogenase contains molybdenum which is present in nitrogen-fixing bacteria. These are also present in leguminous plants.

Uses of Molybdenum

Uses-of-Molybdenum

  • It is mainly alloyed with steel to increase its hardness, toughness, strength, conductivity, and resistivity to corrosion.
  • It is used in electrodes and as a catalyst in the refining of petroleum.
  • Due to its resistivity and strength, it is used in power plants, nuclear reactors, and aircraft engines.
  • Molybdenum sulphide is used as high-temperature lubricant.
  • It is used in making filaments of light bulbs.
  • Molybdenum powders are greatly produced and sold. These are used in circuits, microwave parts, and heat sinks for solids.
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Isotopes of Molybdenum

Molybdenum has 24 isotopes whose half-lives are known with mass numbers from 86 to 110. Naturally occurring molybdenum is a mix of seven isotopes. The most abundant is 98- Mo at 24.1%.

MCQs

  • What is the atomic number of molybdenum?
    • A) 40
    • B) 42
    • C) 44
    • D) 46
    • Answer: B) 42
  • What does the name “Molybdenum” originate from?
    • A) Latin
    • B) Greek
    • C) Sanskrit
    • D) Anglo-Saxon
    • Answer: B) Greek
  • Who separated the metal molybdenum for the first time?
    • A) Carl W. Scheele
    • B) Peter J. Hjelm
    • C) Isaac Newton
    • D) Albert Einstein
    • Answer: B) Peter J. Hjelm
  • What is the primary source of obtaining molybdenum today?
    • A) Graphite
    • B) Wulfenite
    • C) Molybdenite
    • D) Powellite
    • Answer: C) Molybdenite
  • Which metals have higher melting points than molybdenum among the readily available ones?
    • A) Tungsten and Tantalum
    • B) Iron and Copper
    • C) Aluminum and Zinc
    • D) Nickel and Cobalt
    • Answer: A) Tungsten and Tantalum
  • What is the boiling point of molybdenum?
    • A) 2500°C
    • B) 3500°C
    • C) 4639°C
    • D) 5500°C
    • Answer: C) 4639°C
  • How does molybdenum react with oxygen and water at room temperature?
    • A) Reacts vigorously
    • B) Does not react
    • C) Reacts slowly
    • D) Forms a gas
    • Answer: B) Does not react
  • Why is molybdenum considered a toxic element in living organisms?
    • A) Essential for enzymes
    • B) Traces required for proper functioning
    • C) Causes corrosion
    • D) High elastic modulus
    • Answer: A) Essential for enzymes
  • What is the primary use of molybdenum in steel alloys?
    • A) Increase hardness
    • B) Increase conductivity
    • C) Increase malleability
    • D) Increase melting point
    • Answer: A) Increase hardness
  • Where are the major mining areas for molybdenum located?
    • A) USA, Brazil, India
    • B) Chile, Canada, Russia
    • C) China, Australia, South Africa
    • D) Mexico, Argentina, Peru
    • Answer: B) Chile, Canada, Russia
  • What role does molybdenum play in nitrogen-fixing bacteria?
    • A) It is a catalyst
    • B) It is a by-product
    • C) It is a toxic element
    • D) It is present in the enzyme nitrogenase
    • Answer: D) It is present in the enzyme nitrogenase
  • In which industry is molybdenum commonly used due to its resistivity and strength?
    • A) Textile
    • B) Automotive
    • C) Electronics
    • D) Aerospace
    • Answer: D) Aerospace
  • What is the most abundant isotope of naturally occurring molybdenum?
    • A) 92-Mo
    • B) 96-Mo
    • C) 98-Mo
    • D) 102-Mo
    • Answer: C) 98-Mo
  • What is the primary function of molybdenum sulphide?
    • A) Lubricant
    • B) Catalyst
    • C) Insulator
    • D) Conductor
    • Answer: A) Lubricant
  • How many isotopes does molybdenum have, and what is the most abundant naturally occurring isotope?
    • A) 18 isotopes, 102-Mo
    • B) 24 isotopes, 98-Mo
    • C) 30 isotopes, 94-Mo
    • D) 36 isotopes, 100-Mo
    • Answer: B) 24 isotopes, 98-Mo

 

Frequently Asked Questions (FAQs) about Molybdenum: Occurrence, Properties, Uses, and Isotopes

  1. Q: What is the atomic number of molybdenum?
    • A: The atomic number of molybdenum is 42.
  2. Q: Where does the name “Molybdenum” come from?
    • A: The word “Molybdenum” is derived from the Greek word “Molybdos,” which means lead.
  3. Q: Who verified that molybdenite was not graphite and did not contain lead?
    • A: Swedish scientist Carl W. Scheele verified this in 1778.
  4. Q: How was molybdenum first isolated into a metallic form?
    • A: Carl W. Scheele’s friend, Peter J. Hjelm, isolated molybdenum in 1781 by reducing the white solid with carbon.
  5. Q: Where is molybdenum primarily mined today?
    • A: Molybdenum is primarily obtained from ores such as molybdenite, wulfenite, and powellite. Major mining areas include Chile, Canada, and Russia.
  6. Q: What is the melting point of molybdenum?
    • A: The melting point of molybdenum is 2623°C.
  7. Q: Is molybdenum reactive with oxygen and water at room temperature?
    • A: No, molybdenum does not react with oxygen or water at room temperature.
  8. Q: How is molybdenum used in the biological system?
    • A: Although toxic, trace amounts of molybdenum are essential for the proper functioning of enzymes. Approximately 50 enzymes in plants and animals require molybdenum.
  9. Q: What is the primary use of molybdenum in the industry?
    • A: Molybdenum is mainly alloyed with steel to increase its hardness, toughness, strength, conductivity, and resistivity to corrosion.
  10. Q: What is the most abundant naturally occurring isotope of molybdenum?
    • A: The most abundant isotope of naturally occurring molybdenum is 98-Mo, constituting 24.1%.
  11. Q: How many isotopes does molybdenum have, and what are their mass numbers?
    • A: Molybdenum has 24 isotopes with mass numbers ranging from 86 to 110.
  12. Q: Why is molybdenum considered toxic in living organisms?
    • A: While molybdenum is toxic, trace amounts are necessary for living organisms, particularly for the proper functioning of enzymes.
  13. Q: In which industries is molybdenum commonly used due to its resistivity and strength?
    • A: Molybdenum is commonly used in aerospace, power plants, nuclear reactors, and aircraft engines due to its resistivity and strength.
  14. Q: What is the density of molybdenum at room temperature?
    • A: The density of molybdenum is 10.2 grams per cubic centimeter at room temperature.
  15. Q: Can molybdenum be found freely in nature?
    • A: No, molybdenum does not occur freely in nature; it is present in ores and minerals.
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Wrapping up the molybdenum tutorial

The tutorial on Molybdenum provides a comprehensive exploration of the metal’s occurrence, properties, uses, and isotopes.

  1. Introduction:
    • Positioned in group VI B of the periodic table, Molybdenum has an atomic number of 42, an atomic mass of 95.95, and is represented by the symbol “Mo.”
  2. Naming and History:
    • The name “Molybdenum” is derived from the Greek word “Molybdos,” signifying lead. The historical journey involves verification by Carl W. Scheele and subsequent isolation by Peter J. Hjelm.
  3. Occurrence of Molybdenum:
    • Molybdenum is not found freely in nature but in ores and minerals, predominantly sourced from molybdenite, wulfenite, and powellite. Major mining areas include Chile, Canada, and Russia.
  4. Properties of Molybdenum:
    • Silvery-white and harder than tungsten, Molybdenum has a high elastic modulus, does not react with oxygen or water at room temperature, and withstands corrosion. Its melting point is 2623 °C, boiling point is 4639 °C, and density is 10.2 g/cm³.
  5. Molybdenum in Biological System:
    • Despite its toxicity, trace amounts of Molybdenum are crucial for the proper functioning of enzymes. Approximately 50 enzymes in plants and animals rely on Molybdenum.
  6. Uses of Molybdenum:
    • Molybdenum is alloyed with steel for increased hardness, used in electrodes and as a catalyst in petroleum refining. Its resistivity and strength find applications in power plants, nuclear reactors, and aircraft engines. Molybdenum sulfide serves as a high-temperature lubricant, and it is utilized in various technological applications.
  7. Isotopes of Molybdenum:
    • Molybdenum has 24 isotopes, with naturally occurring Molybdenum being a mix of seven isotopes, the most abundant being 98-Mo at 24.1%.
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In summary, the tutorial delivers a comprehensive understanding of Molybdenum, appealing to those interested in its scientific, historical, and practical aspects, making it a valuable resource for learners and enthusiasts.