Molybdenum (Mo): Electron Configuration, Properties and Uses
Molybdenum (Mo): Electron Configuration, Properties and Uses
Electron configuration [Kr] 5s1 4d5 · group 6 · period 5 · Ar 95.95
Molybdenum data
- Atomic number
- 42
- Relative atomic mass
- 95.95
- Group
- 6
- Period
- 5
- Block
- d
- Category
- Transition metal
- Electron configuration
- [Kr] 5s1 4d5
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5
- Electrons per shell
- 2, 8, 18, 13, 1 (K L M N O)
- Valence electrons
- 6
- Electronegativity (Pauling)
- 2.16
- First ionisation energy
- 7.092 eV
- Atomic radius (van der Waals)
- 209 pm
- State at room temperature
- Solid
- Melting point
- 2623 °C
- Boiling point
- 4639 °C
- Density
- 10.2 g/cm³
- Common oxidation states
- +6
- Discovered
- 1778
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 13 · O 1
Orbital diagram (outer electrons)
About molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42. It is a transition metal in group 6, period 5, d-block. Molybdenum was first discovered in 1778. Molybdenum is a solid at room temperature, melting at 2623 °C and boiling at 4639 °C.
Molybdenum electron configuration
The electron configuration of molybdenum is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5, or in short [Kr] 5s1 4d5. Its electrons occupy 5 shells: K = 2, L = 8, M = 18, N = 13, O = 1. For transition metals, valence electrons are counted from the 5s and 4d subshells: 1 + 5 = 6, matching group 6. This is an exception to the Aufbau rule: the usual filling order predicts [Kr] 5s2 4d4, but a half-full 4d subshell is more stable, so an electron moves from the s subshell into 4d.
Filling order: 1s2(2) → 2s2(4) → 2p6(10) → 3s2(12) → 3p6(18) → 4s2(20) → 3d10(30) → 4p6(36) → 5s1(37) → 4d5(42)
Uses of molybdenum
The main uses of molybdenum include high-strength and stainless steels, petroleum desulfurisation catalysts, MoS2 lubricant, and as an enzyme cofactor in plants. For research and analysis you can browse molybdenum compounds in the AMI Scientific catalogue.
Safety
As a solid metal, molybdenum is not especially hazardous. Fine powder can burn, and its compounds should be handled according to their SDS. Always read the safety data sheet (SDS) before working with a chemical.
Other elements in group 6
Frequently asked questions
What is the electron configuration of molybdenum?
The electron configuration of molybdenum (Mo, atomic number 42) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s1 4d5, or [Kr] 5s1 4d5 in short. By shell: 2, 8, 18, 13, 1.
How many valence electrons does molybdenum have?
Molybdenum has 6 valence electrons.
Which group and period is molybdenum in?
Molybdenum is in group 6, period 5, d-block.
What is the atomic mass of molybdenum?
The relative atomic mass of molybdenum is 95.95. Use it to calculate molar mass with the molar mass calculator.
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