Molybdenum (Mo)
Element 42 · Transition metal · atomic mass 95.95 u · group 6, period 5
Electron shells: 2, 8, 18, 13, 1
Molybdenum has one of the highest melting points of any element and keeps steel strong at temperature. It is also an essential trace element for nitrogen-fixing bacteria.
Plants cannot fix nitrogen without molybdenum — the enzyme that does the job needs it.
- Atomic number
- 42
- Atomic mass
- 95.95 u
- Electron configuration
- [Kr] 5s¹ 4d⁵
- Group · period · block
- 6 · 5 · d
- Oxidation states
- +4, +6
- Electronegativity
- 2.16 (Pauling)
- Melting point
- 2,623 °C
- Boiling point
- 4,639 °C
- Density
- 10.2 g/cm³
- State at 20 °C
- Solid
- Appearance
- Grey metallic
- Discovered
- Carl Wilhelm Scheele; isolated by Peter Jacob Hjelm, 1778
42 protons, and 42 electrons when neutral
IUPAC standard atomic weight
Chromium group
What Molybdenum is used for
- High-temperature steel alloys
- Molybdenum disulfide dry lubricant
- Petroleum refining catalysts
- Furnace and filament components
Atomic structure of Molybdenum
A neutral molybdenum atom has 42 protons and 42 electrons. Its most common isotope carries about 54 neutrons, which is where the mass number 96 comes from. Change the neutron count and you have a different isotope of molybdenum; change the proton count and you have a different element entirely.
Those electrons fill shells from the inside out: 2, 8, 18, 13, 1. In orbital notation that is [Kr] 5s¹ 4d⁵. As a d-block element its valence count is variable, which is why it can form compounds in several oxidation states.
3D electron orbitals
See where Molybdenum's electrons actually are — a cloud of 26,000 points sampled from the probability density |ψ|², not a cartoon of a lobe.
Where Molybdenum sits in the periodic table
The d-block. Multiple stable oxidation states give them coloured compounds, catalytic ability and the strength that makes them the working metals of industry.
- Directly above: Chromium — same group, so similar chemistry with a smaller atom.
- Directly below: Tungsten — same group, one shell larger.
- One proton lighter: Niobium.
- One proton heavier: Technetium.
Discovery and naming
Molybdenum was discovered by Carl Wilhelm Scheele; isolated by Peter Jacob Hjelm in 1778. Its name comes from Greek molybdos, "lead".
Keep exploring
Atomic weight from IUPAC/CIAAW; physical properties from PubChem (US National Library of Medicine). Values that have never been measured are shown as “not measured” rather than estimated.
Related Calculators
Frequently Asked Questions
What is the atomic mass of Molybdenum?
The standard atomic weight of Molybdenum is 95.95 u, as published by IUPAC's Commission on Isotopic Abundances and Atomic Weights.
How many protons, neutrons and electrons does Molybdenum have?
Molybdenum has 42 protons, because the atomic number is the proton count and that is what makes an atom Molybdenum at all. A neutral Molybdenum atom has the same number of electrons, 42. The neutron count varies by isotope; the most common one has about 54, since 96 − 42 = 54.
What is the electron configuration of Molybdenum?
The electron configuration of Molybdenum is [Kr] 5s¹ 4d⁵. Its electrons are arranged 2, 8, 18, 13, 1 across 5 shells.
Is Molybdenum a metal?
Yes. Molybdenum is classified as a transition metal, on the metallic side of the table.
What group and period is Molybdenum in?
Molybdenum is in group 6 (the chromium group), period 5, in the d-block. The group is its column and the period is its row.
What is the charge of Molybdenum?
Molybdenum most commonly forms a 6+ or 4+ ion. Like most transition metals it has several accessible oxidation states, so the charge depends on the compound.
What is the melting point of Molybdenum?
Molybdenum melts at 2,623 °C and boils at 4,639 °C. That puts it in the solids at everyday temperatures.
What is Molybdenum used for?
High-temperature steel alloys, Molybdenum disulfide dry lubricant, Petroleum refining catalysts, Furnace and filament components. Molybdenum has one of the highest melting points of any element and keeps steel strong at temperature.
Who discovered Molybdenum, and where does its name come from?
Molybdenum (Mo) was discovered by Carl Wilhelm Scheele; isolated by Peter Jacob Hjelm in 1778. The name comes from Greek molybdos, "lead".