Molybdenum

Molybdenum is a Group 6 chemical element wi the seembol Mo an atomic nummer 42. The name is frae Neo-Laitin Molybdaenum, frae Auncient Greek Μόλυβδος molybdos, meanin leid, syne its ores wur confused wi leid ores. Molybdenum meenerals hae been kent intae prehistory, but the element wis discovered (in the sense o differentiatin it as a new entity frae the mineral sauts o ither metals) in 1778 bi Carl Wilhelm Scheele. The metal wis first isolatit in 1781 bi Peter Jacob Hjelm.

Molybdenum, ₄₂Mo

Molybdenum
Pronunciation	/məˈlɪbdɪnəm/ ​(mə-LIB-din-əm)
Appearance	gray metallic
Standard atomic weight Ar, std(Mo)	7001959500000000000♠95.95(1)
Molybdenum in the periodic cairt
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Airn Cobalt Nickel Capper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Siller (element) Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gowd Mercur (element) Thallium Leid (element) Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium Cr ↑ Mo ↓ W niobium ← molybdenum → technetium
Atomic nummer (Z)	42
Group	group 6
Period	period 5
Block	d-block
Element category	Transeetion metal
Electron confeeguration	[Kr] 4d5 5s1
Electrons per shell	2, 8, 18, 13, 1
Pheesical properties
Phase at STP	solit
Meltin pynt	2896 K ​(2623 °C, ​4753 °F)
Bylin pynt	4912 K ​(4639 °C, ​8382 °F)
Density (near r.t.)	10.28 g/cm3
when liquid (at m.p.)	9.33 g/cm3
Heat o fusion	37.48 kJ/mol
Heat o vapourisation	598 kJ/mol
Molar heat capacity	24.06 J/(mol·K)
Vapour pressur P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 2742 2994 3312 3707 4212 4879
Atomic properties
Oxidation states	−4, −2, −1, 0, +1, +2, +3, +4, +5, +6 strangly acidic
Electronegativity	Pauling scale: 2.16
Atomic radius	empirical: 139 pm
Covalent radius	154±5 pm
Colour lines in a spectral range Spectral lines o molybdenum
Ither properties
Naitural occurrence	primordial
Creestal structur	​body-centred cubic (bcc)
Speed o soond thin rod	5400 m/s (at r.t.)
Thermal expansion	4.8 µm/(m·K) (at 25 °C)
Thermal conductivity	138 W/(m·K)
Thermal diffusivity	54.3 mm2/s (at 300 K)
Electrical resistivity	53.4 n Ω·m (at 20 °C)
Magnetic orderin	paramagnetic
Young's modulus	329 GPa
Shear modulus	126 GPa
Bulk modulus	230 GPa
Poisson ratio	0.31
Mohs haurdness	5.5
Vickers haurdness	1530 MPa
Brinell haurdness	1500 MPa
CAS Nummer	7439-98-7
History
Diskivery	Carl Wilhelm Scheele (1778)
First isolation	Peter Jacob Hjelm (1781)
Main isotopes o molybdenum
Iso­tope Abun­dance Hauf-life (t1/2) Decay mode Pro­duct 92Mo 14.84% >1.9×1020 y (β+β+) 92Zr 93Mo syn 4×103 y ε 93Nb 94Mo 9.25% - (SF) 95Mo 15.92% - (SF) 96Mo 16.68% - (SF) 97Mo 9.55% - (SF) 98Mo 24.13% >1×1014 y β−β− 98Ru 99Mo syn 65.94 h β− 99mTc γ - 100Mo 9.63% 7.8×1018 y (β−β−) 100Ru
Decay modes in parentheses is predict, but hisna yet been observed

Molybdenum disnae occur naiturally as a free metal on Yird, but rather in sindry oxidation states in meenerals. The free element, whilk is a sillery metal wi a gray cast, haes the saxt-heichest meltin pynt o ony element. It readily furms haird, stable carbides in alloys, an for this raison maist o warld production o the element (aboot 80%) is in makin mony types o steel alloys, includin heich strength alloys an superalloys.

Maist molybdenum compounds hae law solubility in watter, but the molybdate ion MoO²⁻
₄ is soluble an furms whan molybdenum-containin meenerals are in contact wi oxygen an watter. Industrially, molybdenum compoonds (aboot 14% o warld production o the element) are uised in high-pressure an heich-temperatur applications, as pigments an catalysts.

Molybdenum-containin enzymes is bi far the maist common catalysts uised bi some bacteria tae break the chemical bond in atmospheric molecular nitrogen, allaein biological nitrogen fixation. At least 50 molybdenum-containin enzymes are nou kent in bacteria an ainimals, tho anly bacterial an cyanobacterial enzymes is involved in nitrogen fixation, an thirnitrogenases contain molybdenum in a different furm frae the rest. Awin tae the diverse functions o the sindry ither types o molybdenum enzymes, molybdenum is a required element for life in aw heicher organisms (eukaryotes), tho nae in aw bacteria.