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Discovery Carl Wilhelm Scheele (1778)
First isolation Peter Jacob Hjelm (1781)
By 1778 Swedish chemist Carl Wilhelm
Scheele stated firmly that molybdena
was (indeed) not galena nor graphite.
Instead, Scheele went further and
correctly proposed that molybdena
was an ore of a distinct new element,
named molybdenum for the mineral in
which it resided, and from which it
might be isolated. Peter Jacob Hjelm
successfully isolated molybdenum by
using carbon and linseed oil in 1781.
the Knaben mine in southern Norway, opened in 1885, was the first dedicated
molybdenum mine. It closed from 1973 to 2007, but is now reopened. Large
mines in Colorado (such as the Henderson mine and the Climax mine)and in
British Columbia yield molybdenite as their primary product, while many
porphyry copper deposits such as the Bingham Canyon Mine in Utah and the
Chuquicamata mine in northern Chile produce molybdenum as a by product
of copper mining.
The Russian Luna 24 mission discovered a molybdenum-bearing grain (1 × 0.6
μm) in a pyroxene fragment taken from Mare Crisium on the Moon. The
comparative rarity of molybdenum in the Earth's crust is offset by its
concentration in a number of water-insoluble ores, often combined with sulfur,
in the same way as copper, with which it is often found. Though molybdenum is
found in such minerals as wulfenite (PbMoO4) and powellite (CaMoO4), the
main commercial source of molybdenum is molybdenite (MoS2). Molybdenum
is mined as a principal ore, and is also recovered as a byproduct of copper and
How to get
In molybdenite processing, the molybdenite is first heated to a temperature of 700 °C (1,292 °F)
and the sulfide is oxidized into molybdenum(VI) oxide by air:
2 MoS2 + 7 O2 → 2 MoO3 + 4 SO2
The oxidized ore is then either heated to 1,100 °C (2,010 °F) to sublimate the oxide, or leached
with ammonia, which reacts with the molybdenum(VI) oxide to form water-soluble molybdates:
MoO3 + 2 NH4OH → (NH4)2(MoO4) + H2O
Copper, an impurity in molybdenite, is less soluble in ammonia. To completely remove it from the
solution, it is precipitated with hydrogen sulfide.
Pure molybdenum is produced by reduction of the oxide with hydrogen, while the molybdenum
for steel production is reduced by the aluminothermic reaction with addition of iron to produce
ferromolybdenum. A common form of ferromolybdenum contains 60% molybdenum.
Melting point 2896 K (2623 °C, 4753 °F)
Boiling point 4912 K (4639 °C, 8382 °F)
Density near r.t. 10.28 g·cm−3
liquid, at m.p. 9.33 g·cm−3
Heat of fusion 37.48 kJ·mol−1
Heat of vaporization 598 kJ·mol−1
Molar heat capacity 24.06 J·mol−1·K−1
With acids & base :
molybdenum does not dissolve in acids or base
With water :
At room temperature, molybdenum does not react with water.
With oxygen :
2 Mo + 3 O2 → 2 MoO3
with the halogens :
Mo(s) + 3F2(g) → MoF6(l) [colourless]
2Mo(s) + 5Cl2(g) → 2MoCl5(s) [black]
Alloys, estimated fractional global industrial use of molybdenum is structural
steel 35%, stainless steel 25%, chemicals 14%, tool & high-speed steels 9%,
cast iron 6%, molybdenum elemental metal 6%, and superalloys, 5%.
Molybdenum powder is used as a fertilizer for some plants, such as
Molybdenum anodes replace tungsten in certain low voltage X-ray
sources, for specialized uses such as mammography.
Molybdenum disilicide (MoSi2) is an electrically conducting ceramic with
primary use in heating elements operating at temperatures above 1500 °C
Molybdenum coated soda lime glass is used for CIGS solar cell fabrication.
Molybdenum dusts and fumes, which can be generated by mining or
metalworking, can be toxic, especially if ingested (including dust trapped
in the sinuses and later swallowed). Low levels of prolonged exposure can
cause irritation to the eyes and skin. Direct inhalation or ingestion of
molybdenum and its oxides should be avoided. OSHA regulations specify
the maximum permissible molybdenum exposure in an 8-hour day as 5
mg/m3. Chronic exposure to 60 to 600 mg/m3 can cause symptoms
including fatigue, headaches and joint pains.
Discovery and first isolation Carlo
Perrier and Emilio Segrè (1937)
From the 1860s through 1871,
early forms of the periodic
table proposed by Dimitri
Mendeleev contained a gap
(element 42) and ruthenium
The discovery of element 43
was finally confirmed in a
December 1936 experiment at
the University of Palermo in
Sicily conducted by Carlo
Perrier and Emilio Segrè.
Prediction by Dmitri
In 1952, astronomer Paul W. Merrill in California detected the spectral signature
of technetium (in particular, light with wavelength of 403.1 nm, 423.8 nm, 426.2
nm, and 429.7 nm) in light from S-type red giants. The stars were near the end of
their lives, yet were rich in this short-lived element, meaning nuclear reactions
within the stars must be producing it. This evidence was used to bolster the then-unproven
theory that stars are where nucleosynthesis of the heavier elements
occurs. More recently, such observations provided evidence that elements
were being formed by neutron capture in the s-process.
Since its discovery, there have been many searches in terrestrial materials for
natural sources of technetium. In 1962, technetium-99 was isolated and
identified in pitchblende from the Belgian Congo in extremely small quantities
(about 0.2 ng/kg); there it originates as a spontaneous fission product of
uranium-238. There is also evidence that the Oklo natural nuclear fission reactor
produced significant amounts of technetium-99, which has since decayed into
How to get
The metastable isotope technetium-99m is continuously produced as a fission product
from the fission of uranium or plutonium in nuclear reactors. Because used fuel is allowed to
stand for several years before reprocessing, all molybdenum-99 and technetium-99m will
have decayed by the time that the fission products are separated from the major
actinides in conventional nuclear reprocessing. The liquid left after plutonium–uranium
extraction (PUREX) contains a high concentration of technetium as TcO−4 but almost all of
this is technetium-99, not technetium-99m.
The vast majority of the technetium-99m used in medical work is produced by irradiating
dedicated highly enriched uranium targets in a reactor, extracting molybdenum-99 from
the targets in reprocessing facilities, and recovering at the diagnostic center the
technetium-99m that is produced upon decay of molybdenum-99. Molybdenum-99 in the
form of molybdate MoO−4 is adsorbed onto acid alumina (AlO) in a shielded column
23chromatograph inside a technetium-99m generator ("technetium cow", also occasionally
called a "molybdenum cow"). Molybdenum-99 has a half-life of 67 hours, so short-lived
technetium-99m (half-life: 6 hours), which results from its decay, is being constantly
produced. The soluble pertechnetate TcO−4 can then be chemically extracted by elution
using a saline solution.
Melting point 2430 K (2157 °C, 3915 °F)
Boiling point 4538 K (4265 °C, 7709 °F)
Density near r.t. 11 g·cm−3
Heat of fusion 33.29 kJ·mol−1
Heat of vaporization 585.2 kJ·mol−1
Molar heat capacity 24.27 J·mol−1·K−1
With base :
Tc2O7 + 2 NaOH → 2 NaTcO4 + H2O
With water :
Technetium does not react with water under normal conditions.
With oxygen :
4 Tc + 7 O2 → 2 Tc2O7
with the halogens :
Tc(s) + 3F2(g) → TcF6(s)
2Tc(s) + 7F2(g) → 2TcF7(s)
with acids :
technetium is insoluble in hydrochloric acid (HCl) and hydrofluoric acid
(HF). It does dissolve in nitric acid, HNO3, or concentrated sulphuric acid,
H2SO4, both of which are oxidizing, to form solutions of pertechnetic acid,
Nuclear medicine and biology
1. Technetium-99m is used in radioactive isotope medical tests, for example as the
radioactive part of a radioactive tracer that medical equipment can detect in the human
2. The longer-lived isotope technetium-95m, with a half-life of 61 days, is used as a
radioactive tracer to study the movement of technetium in the environment and in plant and
Industrial and chemical
1. National Institute of Standards and Technology (NIST) standard beta emitter, and is
therefore used for equipment calibration. Technetium-99 has also been proposed for use in
optoelectronic devices and nanoscale nuclear batteries.
2. technetium can serve as a catalyst. For some reactions, for example the
dehydrogenation of isopropyl alcohol, it is a far more effective catalyst than either rhenium or
Rhenium (Latin: Rhenus meaning: "Rhine") was the last element to be discovered having a
stable isotope (other new radioactive elements have been discovered in nature since
then, such as neptunium and plutonium). The existence of a yet undiscovered element at
this position in the periodic table had been first predicted by Dmitry Mendeleev. Other
calculated information was obtained by Henry Moseley in 1914. It is generally
considered to have been discovered by Walter Noddack, Ida Tacke, and Otto Berg in
Germany. In 1925 they reported that they detected the element in platinum ore and in
the mineral columbite. They also found rhenium in gadolinite and molybdenite. In 1928
they were able to extract 1 g of the element by processing 660 kg of molybdenite. It
was estimated in 1968 that 75% of the rhenium metal in the United States was used for
research and the development of refractory metal alloys. It took several years from that
point on before the super alloys became widely used.
In 1908, Japanese chemist Masataka Ogawa announced that he discovered the 43rd
element and named it nipponium (Np) after Japan (Nippon in Japanese). However, later
analysis indicated the presence of rhenium (element 75), not element 43. The symbol
Np was later used for the element neptunium.
Rhenium is one of the rarest elements in Earth's crust with an average
concentration of 1 ppb other sources quote the number of 0.5 ppb
making it the 77th most abundant element in Earth's crust. Rhenium
is probably not found free in nature (its possible natural occurrence is
uncertain), but occurs in amounts up to 0.2% in the mineral
molybdenite (which is primarily molybdenum disulfide), the major
commercial source, although single molybdenite samples with up to
1.88% have been found.
Chile has the world's largest rhenium reserves, part of the copper ore
deposits, and was the leading producer as of 2005. It was only recently
that the first rhenium mineral was found and described (in 1994), a
rhenium sulfide mineral (ReS2) condensing from a fumarole on Russia's
Kudriavy volcano, Iturup island, in the Kurile Islands. Kudryavy
discharges up to 20–60 kg rhenium per year mostly in the form of
rhenium disulfide. Named rheniite, this rare mineral commands high
prices among collectors.
How to get
Commercial rhenium is extracted from molybdenum roaster-flue gas obtained
from copper-sulfide ores. Some molybdenum ores contain 0.001% to 0.2%
rhenium. Rhenium(VII) oxide and perrhenic acid readily dissolve in water; they
are leached from flue dusts and gasses and extracted by precipitating with
potassium or ammonium chloride as the perrhenate salts, and purified by
Total world production is between 40 and 50 tons/year; the main producers are
in Chile, the United States, Peru, and Poland. Recycling of used Pt-Re catalyst
and special alloys allow the recovery of another 10 tons per year. Prices for the
metal rose rapidly in early 2008, from $1000–$2000 per kg in 2003–2006 to over
$10,000 in February 2008.
The metal form is prepared by reducing ammonium perrhenate with hydrogen
at high temperatures:
2 NH4ReO4 + 7 H2 → 2 Re + 8 H2O + 2 NH3
Melting point 3459 K (3186 °C, 5767 °F)
Boiling point 5869 K (5596 °C, 10105 °F)
Density near r.t. 21.02 g·cm−3
liquid, at m.p. 18.9 g·cm−3
Heat of fusion 60.43 kJ·mol−1
Heat of vaporization 704 kJ·mol−1
Molar heat capacity 25.48 J·mol−1·K−1
rhenium chlorides are ReCl6, ReCl5, ReCl4, and ReCl3
The oxychlorides are most common, and include ReOCl4, ReO3Cl.
oxides include Re2O5, ReO2, and Re2O3.
The sulfides are ReS2 and Re2S7.
Rhenium diboride (ReB2)
With base :
With water :
Rhenium does not react with water under normal conditions.
With oxygen :
4Re(s) + 7O2(g) → 2Re2O7(s)
with the halogens :
Re(s) + 3F2(g) → ReF6(s)
2Re(s) + 7F2(g) → 2ReF7(s)
with acids :
rhenium is insoluble in hydrochloric acid (HCl) and hydrofluoric acid (HF). It does dissolve
in nitric acid, HNO3, or concentrated sulphuric acid, H2SO4, both of which are oxidizing,
to form solutions of perrhenic acid, HReO4.
The Pratt & Whitney F-100 engine uses
CFM International CFM56
jet engine still with blades
made with 3% rhenium
Rhenium in the form of rhenium-platinum
alloy is used as catalyst for
catalytic reforming, which is a
chemical process to convert
petroleum refinery naphthas with
low octane ratings into high-octane
The isotopes 188Re and 186Re are radioactive and
are used for treatment of liver cancer.
188Re is also being used experimentally in a novel
treatment of pancreatic cancer where it is
delivered by means of the bacterium Listeria