Molybdenum

Molybdenum is a chemical element with the symbol Mo and atomic number 42. It is a silvery white metal. The name originates from the Ancient Greek word molybdos meaning lead. This element has the 6th highest meltin point of any element. It forms hard carbides which make it useful in high-strength steel alloys. It is not a __free__ metal on earth, but rather it is found in various oxidation states in minerals. It has low solubility in water.

**History and Uses:** Molybdenum was discovered by Carl Welhelm Scheele, a Swedish chemist, in 1778 in a mineral known as molybdenite (MoS 2 ) which had been confused as a lead compound. Molybdenum was isolated by Peter Jacob Hjelm in 1781. Today, most molybdenum is obtained from molybdenite, wulfenite (PbMoO 4 ) and powellite (CaMoO 4 ). These ores typically occur in conjunction with ores of tin and tungsten. Molybdenum is also obtained as a byproduct of mining and processing tungsten and copper. Molybdenum has a high melting point and is used to make the electrodes of electrically heated glass __furnaces__. Some electrical filaments are also made from molybdenum. The metal is used to make some missile and aircraft parts and is used in the nuclear power industry. Molybdenum is also used as a catalyst in the refining of petroleum. Molybdenum is primarily used as an alloying agent in steel. When added to steel in concentrations between 0.25% and 8%, molybdenum forms ultra-high strength steels that can withstand pressures up to 300,000 pounds per square inch. Molybdenum also improves the strength of steel at high temperatures. When alloyed with nickel, molybdenum forms heat and corrosion resistant materials used in the chemical industry. Molybdenum disulphide (MoS 2 ), one of molybdenum's compounds, is used as a high temperature lubricant. Molybdenum trioxide (MoO 3 ), another molybdenum compound, is used to adhere enamels to metals. Other molybdenum compounds include: molybdic acid (H 2 MoO 4 ), molybdenum hexafluoride (MoF 6 ) and molybdenum phosphide (MoP 2 ).



Harmful effects: Molybdenum is toxic in all but small quantaties. Characteristics: Molybdenum is a silvery-white, high-melting metal. It does not react with [|oxygen] or water at room temperature and it also resists corrosion at ordinary temperatures. Molybdenum is one of the five major refractory metals (metals with very high resistance to heat and wear). The other refactory metals are [|tungsten], [|tantalum], [|rhenium] and [|niobium]. Molybdenum oxide (MoO3) is soluble in __alkaline water__, forming molybdate salts.

Uses of Molybdenum
Molybdenum's strength and resistance to expanding or softening at high temperatures is particularly sought after in critical areas where high temperatures are common, such as in nuclear power plants and aircraft engines. It is also used in the petroleum industry, to catalyze the removal of organic [|sulfur] compounds in coal liquification and gas liquification processes. Molybdenum is an essential trace element for animals and plants. As with [|selenium], too much of it is toxic, too little of it is fatal. In nitrogen fixing bacteria, molybenum is a vital component of the nitrogenase enzyme which allows conversion of [|nitrogen] gas in air into nitrates vital for plant growth. Molybdenum is also present in 20 or so enzymes needed in animals' metabolisms.


 * Symbol:** Mo **Atomic Number:** 42 **Atomic Mass:** 95.94 amu **Melting Point:** 2617.0 °C (2890.15 K, 4742.6 °F) **Boiling Point:** 4612.0 °C (4885.15 K, 8333.6 °F) **Number of Protons/Electrons:** 42 **Number of Neutrons:** 54 **Classification:** Transition Metal **Crystal Structure:** Cubic **Density @ 293 K:** 10.22 g/cm3 **Color:** silverish

Atomic Structure

 * [[image:http://www.chemicalelements.com/bohr/b0042.gif width="309" height="307"]] ||  || **Number of Energy Levels:** 5
 * First Energy Level:** **Second Energy Level:** **Third Energy Level:** **Fourth Energy Level:** **Fifth Energy Level:** ||

Isotopes

 * ** Isotope ** || ** Half Life ** ||
 * Mo-91 || 15.5 minutes ||
 * Mo-92 || Stable ||
 * Mo-93 || 3500.0 years ||
 * Mo-94 || Stable ||
 * Mo-95 || Stable ||
 * Mo-96 || Stable ||
 * Mo-97 || Stable ||
 * Mo-98 || Stable ||
 * Mo-99 || 2.74 days ||
 * Mo-100 || Stable ||
 * Mo-101 || 14.6 minutes ||

Facts

 * Date of Discovery:** 1778 **Discoverer:** Carl Wilhelm Scheele **Name Origin:** From the Greek word //molubdos// (lead) **Uses:** aircraft, missiles **Obtained From:** molybdenite, wulfenite

Molybdenum is a transition metal with an electronegativity of 2.16 on the Pauling scale and a standard atomic weight of 95.96 g/mol. It does not visibly react with oxygen or water at room temperature, and the bulk oxidation occurs at temperatures above 600 °C, resulting in molybdenum trioxide: 2 Mo + 3 O2 → 2 MoO3 The trioxide is volatile and sublimates at high temperatures. This prevents formation of a continuous protective oxide layer, which would stop the bulk oxidation of metal. Molybdenum has several oxidation states, the most stable being +4 and +6 (bolded in the table). The chemistry and the compounds show more similarity to those of tungsten than that of chromium. An example is the instability of molybdenum(III) and tungsten(III) compounds as compared with the stability of the chromium(III) compounds. The highest oxidation state is common in the molybdenum(VI) oxide (MoO3), whereas the normal sulfur compound is molybdenum disulfide MoS2. Molybdenum(VI) oxide is soluble in strong alkaline water, forming molybdates (MoO42−). Molybdates are weaker oxidants than chromates, but they show a similar tendency to form complex oxyanions by condensation at lower pH values, such as [Mo7O24]6− and [Mo8O26]4−. Polymolybdates can incorporate other ions into their structure, forming polyoxometalates. The dark-blue phosphorus-containing heteropolymolybdate P[Mo12O40]3− is used for the spectroscopic detection of phosphorus. The broad range of oxidation states of molybdenum is reflected in various molybdenum chlorides:
 * Chemical Symbol: ||  || Mo ||
 * Atomic Number: ||  || 42 ||
 * Atomic Weight: ||  || 95.9 ||
 * Melting Point: ||  || 2620 °C ||
 * Boiling Point: ||  || 4830 °C ||
 * Density of Solid: ||  || 10222 kg m-3 ||
 * Electron Configuration: ||  || 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d5 5s1 ||
 * __Chemical Compounds__**

Abundance

 * [|Amount in average human body (70kg):] ||  || 0.0093 g ||
 * Average amount in Earth's crust: ||  || 1.2 ppm by mass ||
 * [|Average amount in seawater:] ||  || 0.01 mg L-1 ||