42
Mo
Molybdenum
95.95
Molybdenum (Mo)
Transition MetalGroup 6Period 5d-block-block
Molybdenum is a chemical element with symbol Mo and atomic number 42. The name is from Neo-Latin molybdaenum, from Ancient Greek Μόλυβδος molybdos, meaning lead, since its ores were confused with lead ores. Molybdenum minerals have been known throughout history, but the element was discovered (in the sense of differentiating it as a new entity from the mineral salts of other metals) in 1778 by Carl Wilhelm Scheele.
Latin name: Molybdaenum
Atomic Number
42
Atomic Mass
95.95 g/mol
Phase (STP)
Solid
Electron Config.
[Kr] 4d⁵ 5s¹
General
SymbolMo
Atomic Number42
Atomic Mass95.95 g/mol
CategoryTransition Metal
Group6
Period5
Blockd-block
Electron Configuration[Kr] 4d⁵ 5s¹
Valence Electrons6
Coloursilvery-gray metallic
Appearancegray metallic
CAS NumberCAS7439-98-7
Physical Properties
Phase (STP)Solid
Density10.28 g/cm³
Melting Point2622.85°C · 4753.13°F · 2896.00 K
Boiling Point4638.85°C · 8381.93°F · 4912.00 K
Atomic Properties
Atomic Radius190 pm
Electronegativity2.16 Pauling
Ionization Energy684 kJ/mol
Oxidation States+6, +5, +4, +3, +2
Ion ChargeMo3+/Mo4+/Mo6+
Thermodynamic
Molar Heat24.06 J/(mol·K)
Crystal Structure
Crystal Structurebody-centered cubic
Mechanical Properties
Mohs Hardness5.5
Abundance
In Universe0.00001%
In Sun0.000009%
In Earth's Crust0.0012%
In Oceans0.0000003%
In Humans0.000013%
In Meteorites0.00004%
Discovery & History
Discovery Year1778
Discovered ByCarl Wilhelm Scheele
Country of DiscoverySweden
Isotopes of Molybdenum
| Isotope | Abundance | Half-life | Decay |
|---|---|---|---|
| Mo-92 | 14.53% | Stable | — |
| Mo-94 | 9.15% | Stable | — |
| Mo-95 | 15.84% | Stable | — |
| Mo-96 | 16.67% | Stable | — |
| Mo-97 | 9.6% | Stable | — |
| Mo-98 | 24.39% | Stable | — |
| Mo-100 | 9.82% | 7.1 × 10¹⁸ years | β⁻β⁻ |