#42 / 118
42Mo95.95
Transition Metalssolid at STPD-block

Molybdenum

Group: 6•Period: 5•Standard Atomic Weight: 95.95 u
Open Full Periodic TableView Bohr Model

Why is Molybdenum in this position?

Understanding the scientific rationale behind Molybdenum's position in the periodic table:

Group Assignment
Group 6

Belongs to Group 6 because it has 6 valence electrons (4d⁵ 5s¹).

Period Assignment
Period 5

Belongs to Period 5 because its outermost electron occupies n=5.

Orbital Block
D-block

Belongs to the d-block because its valence electrons fill the 4d subshell.

Chemical Category
Transition Metals

Classified as a transition metal with extreme heat resistance and variable oxidation chemistry.

Atomic Structure & Bohr Shell Model

Shell Distribution: [2, 8, 18, 13, 1]

Bohr Atomic Shell Model(2, 8, 18, 13, 1)

Hover or tap any shell orbit ring to inspect electron counts and 2n² capacities.

42 Protons (p⁺)54 Neutrons (n⁰)
KShell K: Electron 1 of 2Shell K: Electron 2 of 2LShell L: Electron 1 of 8Shell L: Electron 2 of 8Shell L: Electron 3 of 8Shell L: Electron 4 of 8Shell L: Electron 5 of 8Shell L: Electron 6 of 8Shell L: Electron 7 of 8Shell L: Electron 8 of 8MShell M: Electron 1 of 18Shell M: Electron 2 of 18Shell M: Electron 3 of 18Shell M: Electron 4 of 18Shell M: Electron 5 of 18Shell M: Electron 6 of 18Shell M: Electron 7 of 18Shell M: Electron 8 of 18Shell M: Electron 9 of 18Shell M: Electron 10 of 18Shell M: Electron 11 of 18Shell M: Electron 12 of 18Shell M: Electron 13 of 18Shell M: Electron 14 of 18Shell M: Electron 15 of 18Shell M: Electron 16 of 18Shell M: Electron 17 of 18Shell M: Electron 18 of 18NShell N: Electron 1 of 13Shell N: Electron 2 of 13Shell N: Electron 3 of 13Shell N: Electron 4 of 13Shell N: Electron 5 of 13Shell N: Electron 6 of 13Shell N: Electron 7 of 13Shell N: Electron 8 of 13Shell N: Electron 9 of 13Shell N: Electron 10 of 13Shell N: Electron 11 of 13Shell N: Electron 12 of 13Shell N: Electron 13 of 13OShell O: Electron 1 of 1MoZ = 42

Educational Note: This Niels Bohr planetary model visually illustrates principal quantum energy shells ($n=1, 2, 3\dots$) and electron counts. In modern quantum mechanics (Schrödinger model), electrons do not orbit in fixed circular planetary tracks, but exist as 3D probability clouds (orbitals: $s, p, d, f$) governed by the Heisenberg uncertainty principle.

Electron Shell Filling Breakdown

Shell K (n=1):2 / 2 electrons (100%)
Shell L (n=2):8 / 8 electrons (100%)
Shell M (n=3):18 / 18 electrons (100%)
Shell N (n=4):13 / 32 electrons (41%)
Shell O (n=5):1 / 50 electrons (2%)
Aufbau Electron Configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d⁵ 5s¹

Neutral ground state configuration. Valence electrons: 6.

Atomic & Quantum Properties

Electronegativity (Pauling)2.16 Pauling
1st Ionization Energy684.3 kJ/mol
Electron Affinity-71.9 kJ/mol
Atomic Radius (empirical)190 pm
Common Oxidation States+6, +4
Crystal StructureBCC

Physical & Thermal Properties

Density at STP10.28 g/cm³
Melting Point2623 °C (2896 K)
Boiling Point4639 °C (4912 K)
Magnetic OrderingParamagnetic
Discovery Year1778
Discovered ByCarl Wilhelm Scheele

Real-World Uses, Occurrence & Compounds

Major Industrial & Everyday Uses
  • Ultra-hard high-temperature structural alloy steels and armor plating
  • Molybdenum disulfide (MoS₂) dry solid lubricant for vacuum and aerospace bearings
  • Petroleum hydrodesulfurization catalysts removing sulfur from crude oil
  • Molybdenum-99 production, the parent isotope of medical imaging workhorse Technetium-99m
Occurrence in Nature

Mined from molybdenite ore (MoS₂) and wulfenite (PbMoO₄), frequently as a coproduct of copper mining.

Etymology & Name Origin

From Greek 'molybdos' meaning lead, because its ore molybdenite was confused with lead ore

Important Chemical Compounds
MoS₂ (Molybdenum disulfide)
MoO₃ (Molybdenum trioxide)
Na₂MoO₄ (Sodium molybdate)
Interesting Chemical Facts
  • • Like chromium, molybdenum features a half-filled d-subshell configuration ([Kr] 4d⁵ 5s¹) for maximum exchange energy stabilization.
  • • The nitrogenase enzyme in nitrogen-fixing soil bacteria contains a molybdenum-iron cluster (FeMo-cofactor) that enables plants to capture atmospheric N₂.
  • • Molybdenum disulfide (MoS₂) has a layered graphene-like structure that shears easily, lubricating machinery even in the vacuum of space where oils boil away.
Safety & Handling Note

Essential micronutrient for plants and animals, but high doses cause molybdenum toxicity (molybdenosis) and copper deficiency.

Explore Neighborhood Elements

Same Group (Group 6):
#24Cr#74W#106Sg
Same Period (Period 5):
#37Rb#38Sr#39Y#40Zr#41Nb#43Tc#44Ru#45Rh#46Pd#47Ag#48Cd#49In#50Sn#51Sb#52Te#53I#54Xe