Difference between revisions of "Protactinium" - New World Encyclopedia
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== Occurrence == | == Occurrence == | ||
− | The isotope protactinium-231 occurs in [[uraninite|pitchblende]] to the extent of about 1 [[parts per million|part]] per 10 million parts of ore. Some ores from the [[Democratic Republic of the Congo]] have about 3 parts per million (ppm). | + | The isotope protactinium-231 occurs in [[uraninite|pitchblende]] to the extent of about 1 [[parts per million|part]] per 10 million parts of ore. Some ores from the [[Democratic Republic of the Congo]] have been found to contain the element at a concentration of about 3 parts per million (ppm). |
== History == | == History == | ||
Line 49: | Line 49: | ||
The existence of an element between [[thorium]] and [[uranium]] was [[Mendeleev's predicted elements|predicted to exist]] by [[Dmitri Mendeleev]] in 1871. In 1900, [[William Crookes]] isolated [[protactinium]] as a radioactive material from uranium, but he could not identify the material<ref> {{cite book | last = Emsley | first = John | title = Nature's Building Blocks | edition = (Hardcover, First Edition) | publisher = [[Oxford University Press]] | date = 2001 | pages = page 347 | id = ISBN 0198503407 }}</ref>. | The existence of an element between [[thorium]] and [[uranium]] was [[Mendeleev's predicted elements|predicted to exist]] by [[Dmitri Mendeleev]] in 1871. In 1900, [[William Crookes]] isolated [[protactinium]] as a radioactive material from uranium, but he could not identify the material<ref> {{cite book | last = Emsley | first = John | title = Nature's Building Blocks | edition = (Hardcover, First Edition) | publisher = [[Oxford University Press]] | date = 2001 | pages = page 347 | id = ISBN 0198503407 }}</ref>. | ||
− | Protactinium was first identified in 1913, when [[Kasimir Fajans]] and [[O. H. Göhring]] encountered short-lived isotope 234m-Pa, with a half-life of about 1.17 minutes, during their studies of the decay chain of 238-U. They gave the new element the name ''Brevium'' ([[Latin]] ''brevis'', brief, short) | + | Protactinium was first identified in 1913, when [[Kasimir Fajans]] and [[O. H. Göhring]] encountered short-lived isotope 234m-Pa, with a half-life of about 1.17 minutes, during their studies of the decay chain of 238-U. They gave the new element the name ''Brevium'' ([[Latin]] ''brevis'', brief, short). The name was changed to ''Protoactinium'' in 1918, when two groups of scientists ([[Otto Hahn]] and [[Lise Meitner]] of [[Germany]] and [[Frederick Soddy]] and [[John Cranston]] of the [[United Kingdom|UK]]) independently discovered 231-Pa. The name was shortened to ''Protactinium'' in 1949. |
− | [[Aristid V. Grosse]] prepared 2 mg of Pa<sub>2</sub>O<sub>5</sub> in 1927, and later on managed to isolate | + | [[Aristid V. Grosse]] prepared 2 milligrams (mg) of Pa<sub>2</sub>O<sub>5</sub> in 1927, and later on managed to isolate protactinium for the first time in 1934 from 0.1 mg of Pa<sub>2</sub>O<sub>5</sub>, first converting the oxide to an iodide and then cracking it in a high vacuum by an electrically heated filament by the reaction 2PaI<sub>5</sub> → 2Pa + 5I<sub>2</sub>. |
− | In 1961, the United Kingdom Atomic Energy Authority was able to produce 125 g of 99.9% pure protactinium, after processing 60 tons of waste material in a 12-stage process and spending 500,000 USD. This was the world's only supply of the element for many years to come, and it has been reported that the metal | + | In 1961, the United Kingdom Atomic Energy Authority was able to produce 125 g of 99.9% pure protactinium, after processing 60 tons of waste material in a 12-stage process and spending 500,000 USD. This was the world's only supply of the element for many years to come, and it has been reported that the metal was sold to laboratories at a price of 2,800 USD per gram. |
== Notable Characteristics == | == Notable Characteristics == | ||
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* Fluorides: | * Fluorides: | ||
− | ** [[protactinium(IV) fluoride | + | ** [[protactinium(IV) fluoride]] (PaF<sub>4</sub>) |
− | ** [[protactinium(V) fluoride | + | ** [[protactinium(V) fluoride]] (PaF<sub>5</sub>) |
* Chlorides: | * Chlorides: | ||
− | ** [[protactinium(IV) chloride | + | ** [[protactinium(IV) chloride]] (PaCl<sub>4</sub>) |
− | ** [[protactinium(V) chloride | + | ** [[protactinium(V) chloride]] (PaCl<sub>5</sub>) |
* Bromides: | * Bromides: | ||
− | ** [[protactinium(IV) bromide | + | ** [[protactinium(IV) bromide]] (PaBr<sub>4</sub>) |
− | ** [[protactinium(V) bromide | + | ** [[protactinium(V) bromide]] (PaBr<sub>5</sub>) |
* Iodides: | * Iodides: | ||
− | ** [[protactinium(III) iodide | + | ** [[protactinium(III) iodide]] (PaI<sub>3</sub>) |
− | ** [[protactinium(IV) iodide | + | ** [[protactinium(IV) iodide]] (PaI<sub>4</sub>) |
− | ** [[protactinium(V) iodide | + | ** [[protactinium(V) iodide]] (PaI<sub>5</sub>) |
* Oxides: | * Oxides: | ||
** [[protactinium(II) oxide]] (PaO) | ** [[protactinium(II) oxide]] (PaO) |
Revision as of 07:11, 10 March 2007
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General | ||||||||||||||||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Name, Symbol, Number | protactinium, Pa, 91 | |||||||||||||||||||||||||||
Chemical series | actinides | |||||||||||||||||||||||||||
Group, Period, Block | n/a, 7, f | |||||||||||||||||||||||||||
Appearance | bright, silvery metallic luster | |||||||||||||||||||||||||||
Atomic mass | 231.03588(2) g/mol | |||||||||||||||||||||||||||
Electron configuration | [Rn] 5f2 6d1 7s2 | |||||||||||||||||||||||||||
Electrons per shell | 2, 8, 18, 32, 20, 9, 2 | |||||||||||||||||||||||||||
Physical properties | ||||||||||||||||||||||||||||
Phase | solid | |||||||||||||||||||||||||||
Density (near r.t.) | 15.37 g/cm³ | |||||||||||||||||||||||||||
Melting point | 1841 K (1568 °C, 2854 °F) | |||||||||||||||||||||||||||
Boiling point | ? 4300 K (? 4027 °C, ? °F) | |||||||||||||||||||||||||||
Heat of fusion | 12.34 kJ/mol | |||||||||||||||||||||||||||
Heat of vaporization | 481 kJ/mol | |||||||||||||||||||||||||||
Atomic properties | ||||||||||||||||||||||||||||
Crystal structure | orthorhombic | |||||||||||||||||||||||||||
Oxidation states | 2, 3, 4, 5 (weakly basic oxide) | |||||||||||||||||||||||||||
Electronegativity | 1.5 (Pauling scale) | |||||||||||||||||||||||||||
Ionization energies | 1st: 568 kJ/mol | |||||||||||||||||||||||||||
Atomic radius | 180 pm | |||||||||||||||||||||||||||
Miscellaneous | ||||||||||||||||||||||||||||
Magnetic ordering | no data | |||||||||||||||||||||||||||
Electrical resistivity | (0 °C) 177 nΩ·m | |||||||||||||||||||||||||||
Thermal conductivity | (300 K) 47 W/(m·K) | |||||||||||||||||||||||||||
CAS registry number | 7440-13-3 | |||||||||||||||||||||||||||
Notable isotopes | ||||||||||||||||||||||||||||
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Protactinium (chemical symbol Pa, atomic number 91) is a member of the actinide series of chemical elements.
Occurrence
The isotope protactinium-231 occurs in pitchblende to the extent of about 1 part per 10 million parts of ore. Some ores from the Democratic Republic of the Congo have been found to contain the element at a concentration of about 3 parts per million (ppm).
History
The existence of an element between thorium and uranium was predicted to exist by Dmitri Mendeleev in 1871. In 1900, William Crookes isolated protactinium as a radioactive material from uranium, but he could not identify the material[1].
Protactinium was first identified in 1913, when Kasimir Fajans and O. H. Göhring encountered short-lived isotope 234m-Pa, with a half-life of about 1.17 minutes, during their studies of the decay chain of 238-U. They gave the new element the name Brevium (Latin brevis, brief, short). The name was changed to Protoactinium in 1918, when two groups of scientists (Otto Hahn and Lise Meitner of Germany and Frederick Soddy and John Cranston of the UK) independently discovered 231-Pa. The name was shortened to Protactinium in 1949.
Aristid V. Grosse prepared 2 milligrams (mg) of Pa2O5 in 1927, and later on managed to isolate protactinium for the first time in 1934 from 0.1 mg of Pa2O5, first converting the oxide to an iodide and then cracking it in a high vacuum by an electrically heated filament by the reaction 2PaI5 → 2Pa + 5I2.
In 1961, the United Kingdom Atomic Energy Authority was able to produce 125 g of 99.9% pure protactinium, after processing 60 tons of waste material in a 12-stage process and spending 500,000 USD. This was the world's only supply of the element for many years to come, and it has been reported that the metal was sold to laboratories at a price of 2,800 USD per gram.
Notable Characteristics
Protactinium is a silver metallic element that belongs to the actinide group, with a bright metallic luster that it retains for some time in the air. It is superconductive at temperatures below 1.4 K.
Isotopes
Many radioisotopes of protactinium have been characterized. The most stable of these are 231-Pa, with a half-life of 32,760 years; 233-Pa, with a half-life of 26.967 days; and 230-Pa, with a half-life of 17.4 days. All the remaining radioactive isotopes have half-lives that are less than 1.6 days, and the majority of these have half-lives that are less than 1.8 seconds. This element also has 2 meta states, 217m-Pa (t½ 1.15 milliseconds) and 234m-Pa (t½ 1.17 minutes).
The primary decay mode before the most stable isotope, 231-Pa, is alpha decay and the primary mode after is beta minus decay. The primary decay products before 231-Pa are actinium isotopes, and the primary products after are uranium isotopes.
Compounds
Known compounds of protactinium include the following:
- Fluorides:
- protactinium(IV) fluoride (PaF4)
- protactinium(V) fluoride (PaF5)
- Chlorides:
- protactinium(IV) chloride (PaCl4)
- protactinium(V) chloride (PaCl5)
- Bromides:
- protactinium(IV) bromide (PaBr4)
- protactinium(V) bromide (PaBr5)
- Iodides:
- protactinium(III) iodide (PaI3)
- protactinium(IV) iodide (PaI4)
- protactinium(V) iodide (PaI5)
- Oxides:
- protactinium(II) oxide (PaO)
- protactinium(IV) oxide (PaO2)
- protactinium(V) oxide (Pa2O5)
Applications
Given its scarcity, high radioactivity, and toxicity, there are currently no uses for protactinium outside of basic scientific research.
Protactinium-231, which is formed by the alpha decay of uranium-235, could possibly sustain a nuclear chain reaction and might, in principle, be used to build a nuclear weapon. The critical mass, according to Walter Seifritz, is 750±180 kilograms (kg). Other authors conclude that no chain reactions are possible in protactinium-231.
Precautions
Protactinium is both toxic and highly radioactive. It requires precautions similar to those used when handling plutonium.
Notes
- ↑ Emsley, John (2001). Nature's Building Blocks, (Hardcover, First Edition), Oxford University Press, page 347. ISBN 0198503407.
ReferencesISBN links support NWE through referral fees
- "Protactinium" Los Alamos National Laboratory. Retrieved March 10, 2007.
- Chang, Raymond (2006). Chemistry (ninth ed.) New York: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
- Greenwood, N.N.; and Earnshaw, A. (1998). Chemistry of the Elements (2nd Edition). Oxford, U.K.; Burlington, Massachusetts: Butterworth-Heinemann, Elsevier Science. ISBN 0750633654. Online version.
- Cotton, F. Albert; and Wilkinson, Geoffrey (1980). Advanced Inorganic Chemistry (4th ed.), New York:Wiley. ISBN 0-471-02775-8.
- Protactinium WebElements.com. Retrieved March 10, 2007.
External links
- Protactinium WebElements.com.
- Protactinium It's Elemental.
- [1] InfoHaunter
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