Molybdenum (Mo)

Gray metallic

Molybdenum is a refractory metal that strengthens steel and is an essential trace nutrient for nitrogen-fixing bacteria, and with [Kr] 4d⁵ 5s¹ (half-filled d-shell), molybdenum has one of the highest melting points of any element (2896 K). It is a cofactor in nitrogenase, the enzyme that fixes atmospheric N₂.

Key metrics

Density10.28g/cm³

Melting point2,896K

Boiling point4,912K

Electronegativity2.16Pauling

Discovery

1778discovered

Discovered by: Carl Wilhelm Scheele
Reactivity profile: Stable at high temperatures
Reactivity: Low
Bonding: Metallic

Electron configuration

\textcolor{#6b7280}{[Kr]}\; \textcolor{#22c55e}{4_{d}^{5}}\; \textcolor{#ef4444}{5_{s}^{1}}

[Kr] 4d5 5s1

Wave function

\Psi_{\text{Mo}} \approx \frac{1}{\sqrt{42!}} \det \left| \chi_1(\mathbf{r}_1) \dots \chi_{42}(\mathbf{r}_{42}) \right|

Probability density $|\Psi|^2$ across the Mo valence shell.

Crystal structure

Body-Centered Cubic

Lattice constantsa = 1.00

Cell anglesα = β = γ = 90°

Coordination number8

Atoms per cell2

Atomic packing factor0.68

Physical properties

Atomic radius: 139 pm
Ionization energy: 684 kJ/mol
Electron affinity: 72 kJ/mol
Crystal structure: Body-centered cubic (bcc)

Oxidation states

+2+4+6

Acid/base

Basic

Strongly acidicStrongly basic

State at 25 °CSolid

2896 K4912 K298 K

Emission spectrum

3 transitions

380450500550600650700780

VioletBlueGreenYellowRed

489.2nmMo IBlue50%

550.6nmMo I (green)Green100%

588.8nmMo I (yellow)Yellow70%

Dominant line 550.6 nmRange 489–589 nmTransitions 3