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In its pure form, molybdenum is a silvery-grey metal with a Mohs hardness of 5.5 and a standard atomic weight of 95.95 g/mol. [ 15][ 16] It has a melting point of 2,623 °C (4,753 °F), sixth highest of the naturally occurring elements; only tantalum, osmium, rhenium, tungsten, and carbon have higher melting points. [ 9]
The molybdenum cofactor (pictured) is composed of a molybdenum-free organic complex called molybdopterin, which has bound an oxidized molybdenum (VI) atom through adjacent sulfur (or occasionally selenium) atoms. Except for the ancient nitrogenases, all known Mo-using enzymes use this cofactor. Molybdate is transported in the body as MoO 42−.
Tellurium is a chemical element; it has symbol Te and atomic number 52. It is a brittle, mildly toxic, rare, silver-white metalloid. Tellurium is chemically related to selenium and sulfur, all three of which are chalcogens. It is occasionally found in its native form as elemental crystals. Tellurium is far more common in the Universe as a whole ...
The agriculture industry uses 500 tons per year as a fertilizer. In particular, its use has been suggested for treatment of whiptail in broccoli and cauliflower in molybdenum-deficient soils. [4] [5] However, care must be taken because at a level of 0.3 ppm sodium molybdate can cause copper deficiencies in animals, particularly cattle. [3]
Molybdenum-100, with a half-life of approximately 8.5×10 18 y, is the only naturally occurring radioisotope. It undergoes double beta decay into ruthenium-100. Molybdenum-98 is the most common isotope, comprising 24.14% of all molybdenum on Earth. Molybdenum isotopes with mass numbers 111 and up all have half-lives of approximately .15 s. [5]
Biological roles of the elements. A large fraction of the chemical elements that occur naturally on the Earth's surface are essential to the structure and metabolism of living things. Four of these elements (hydrogen, carbon, nitrogen, and oxygen) are essential to every living thing and collectively make up 99% of the mass of protoplasm. [ 1]
The discrete molybdenum oxyanions range in size from the simplest MoO 2− 4, found in potassium molybdate up to extremely large structures found in isopoly-molybdenum blues that contain for example 154 Mo atoms. The behaviour of molybdenum is different from the other elements in group 6. Chromium only forms the chromates, CrO 2− 4, Cr 2 O 2 ...
Molybdenite is an important ore of molybdenum, and is the most common source of the metal. [4] While molybdenum is rare in the Earth's crust, molybdenite is relatively common and easy to process, and accounts for much of the metal's economic viability. Molybdenite is purified by froth flotation, and then oxidized to form soluble molybdate ...