Molybdenum (Mo)
Transition metal
Molybdenum is a refractory metal that keeps its strength red-hot, hardening the steels in engines, drills and armour. Living cells also rely on it: molybdenum enzymes let organisms process nitrogen.
Position on the periodic table
Atomic properties
| Atomic number | 42 |
|---|---|
| Atomic mass | 95.951 amu |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5 |
| Noble gas shorthand | [Kr] 4d5 5s1 |
| Electrons per shell | 2, 8, 18, 13, 1 |
| Valence electrons (outer shell) | 1 |
| Common oxidation states | +6, +4 |
| Electronegativity (Pauling) | 2.16 |
| Covalent radius (approx.) | 154 pm |
| First ionization energy | 684.3 kJ/mol |
| Electron affinity | 72.1 kJ/mol |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Density | 10.28 g/cm³ |
| Melting point | 2622.8 °C (2896 K) |
| Boiling point | 4638.9 °C (4912 K) |
| Appearance | gray metallic |
| Radioactive | No |
| Origin | Occurs naturally |
Electron configuration of molybdenum
Molybdenum's ground-state electron configuration is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5, usually shortened to [Kr] 4d5 5s1. Its electrons occupy 5 shells (2, 8, 18, 13, 1), placing it in period 5 of the d-block. Explore it interactively in the electron configuration calculator.
Uses of molybdenum
- High-strength and stainless steels
- High-temperature furnace parts
- Solid lubricant (MoS₂)
- Catalysts for removing sulfur from fuels
Biological role: Essential trace element for nearly all life — key enzymes in nitrogen metabolism contain it.
Occurrence: Mined as molybdenite (MoS₂), often alongside copper.
Common compounds of molybdenum
MoS2
Molybdenum disulfide
MoO3
Molybdenum trioxide
History and discovery
Discovered: 1778 — Carl Wilhelm Scheele. Name origin: From Greek molybdos, meaning lead — its ore was long confused with lead and graphite.
Carl Wilhelm Scheele distinguished molybdenite from graphite in 1778; Peter Jacob Hjelm isolated the metal in 1781.
Safety notes
Low toxicity in normal exposure; dusts and fumes need industrial controls.
Educational context only — always follow your school's laboratory rules and never handle chemicals without proper supervision. See our disclaimer.
Practice questions
Quick practice: Molybdenum
1. What is the chemical symbol of Molybdenum?
2. What is the atomic number of Molybdenum?
3. Which category does Molybdenum belong to?
4. What is the state of Molybdenum at room temperature?
5. Which period of the periodic table is Molybdenum in?
Molybdenum FAQs
What is the atomic number of molybdenum?
Molybdenum's atomic number is 42 — every molybdenum atom has 42 protons in its nucleus.
What is the symbol for molybdenum?
Mo. From Greek molybdos, meaning lead — its ore was long confused with lead and graphite.
Is molybdenum a metal, nonmetal, or metalloid?
Molybdenum is classified as a transition metal.
What state is molybdenum at room temperature?
At about 25 °C, molybdenum is a solid. It melts at 2622.8 °C.
What is molybdenum used for?
Key uses include: high-strength and stainless steels; high-temperature furnace parts; solid lubricant (mos₂).
Related elements
Keep working with this element
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