Difference between revisions of "Protactinium" - New World Encyclopedia

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'''Protactinium''' ([[International Phonetic Alphabet|IPA]]: {{IPA|/ˌprəʊˌtakˈtɪniəm/}}) is a [[chemical element]] in the [[periodic table]] that has the symbol '''Pa''' and [[atomic number]] 91.
+
'''Protactinium''' (chemical symbol '''Pa''', [[atomic number]] 91) is a member of the [[actinide]] series of [[chemical element]]s.
  
== Notable Characteristics ==
+
== Occurrence ==
Protactinium is a silver [[metal]]lic element that belongs to the [[actinide]] group, with a bright metallic luster that it retains for some time in the air. It is [[Superconductivity|superconductive]] at temperatures below 1.4 K.
+
 
 +
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).
 +
 
 +
== History ==
 +
 
 +
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); 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, and shortened to ''Protactinium'' in 1949.
  
== Applications ==
+
[[Aristid V. Grosse]] prepared 2 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>.
Due to 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 kg. Other authors conclude that no chain reactions are possible in Protactinium-231.
+
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 subsequently was sold to laboratories for a cost of 2,800 USD per gram.
  
== History ==
+
== Notable Characteristics ==
The existence of an element between [[thorium]] and [[uranium]] was [[Mendeleev's predicted elements|predicted to exist]] by [[Dmitri Mendeleev|Mendeleev]] in [[1871]]. In [[1900]] [[William Crookes]] isolated [[protactinium]] as a radioactive material from uranium which he could not identify<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); 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, and shortened to ''Protactinium'' in [[1949]].
+
Protactinium is a silver [[metal]]lic element that belongs to the [[actinide]] group, with a bright metallic luster that it retains for some time in the air. It is [[Superconductivity|superconductive]] at temperatures below 1.4 K.
  
[[Aristid V. Grosse]] prepared 2 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>.
+
=== Isotopes ===
  
In [[1961]], the United Kingdom Atomic Energy Authority was able to produce 125 g of 99.9% pure protactinium, 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 is reported that the metal was sold to laboratories for a cost of 2,800 USD / g in the following years.
+
Many [[radioisotope]]s 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 state]]s, 217m-Pa (t<sub>½</sub> 1.15 milliseconds) and 234m-Pa (t<sub>½</sub> 1.17 minutes).
  
== Occurrence ==
+
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 product]]s before 231-Pa are [[actinium]] isotopes, and the primary products after are [[uranium]] isotopes.
Protactinium occurs in [[uraninite|pitchblende]] to the extent of about 1 [[parts per million|part]] <sup>231</sup>Pa to 10 million of ore.  Some ores from the [[Democratic Republic of the Congo]] have about 3 ppm.
 
  
 
== Compounds ==
 
== Compounds ==
Known protactinium compounds:
+
Known compounds of protactinium include the following:
  
* Fluorides
+
* Fluorides:
 
** [[protactinium(IV) fluoride|PaF<sub>4</sub>]]
 
** [[protactinium(IV) fluoride|PaF<sub>4</sub>]]
 
** [[protactinium(V) fluoride|PaF<sub>5</sub>]]
 
** [[protactinium(V) fluoride|PaF<sub>5</sub>]]
* Chlorides
+
* Chlorides:
 
** [[protactinium(IV) chloride|PaCl<sub>4</sub>]]
 
** [[protactinium(IV) chloride|PaCl<sub>4</sub>]]
 
** [[protactinium(V) chloride|PaCl<sub>5</sub>]]
 
** [[protactinium(V) chloride|PaCl<sub>5</sub>]]
* Bromides
+
* Bromides:
 
** [[protactinium(IV) bromide|PaBr<sub>4</sub>]]
 
** [[protactinium(IV) bromide|PaBr<sub>4</sub>]]
 
** [[protactinium(V) bromide|PaBr<sub>5</sub>]]
 
** [[protactinium(V) bromide|PaBr<sub>5</sub>]]
* Iodides
+
* Iodides:
 
** [[protactinium(III) iodide|PaI<sub>3</sub>]]
 
** [[protactinium(III) iodide|PaI<sub>3</sub>]]
 
** [[protactinium(IV) iodide|PaI<sub>4</sub>]]
 
** [[protactinium(IV) iodide|PaI<sub>4</sub>]]
 
** [[protactinium(V) iodide|PaI<sub>5</sub>]]
 
** [[protactinium(V) iodide|PaI<sub>5</sub>]]
* Oxides
+
* Oxides:
** [[protactinium(II) oxide|PaO]]
+
** [[protactinium(II) oxide]] (PaO)
** [[protactinium(IV) oxide|PaO<sub>2</sub>]]
+
** [[protactinium(IV) oxide]] (PaO<sub>2</sub>)
** [[protactinium(V) oxide|Pa<sub>2</sub>O<sub>5</sub>]]
+
** [[protactinium(V) oxide]] (Pa<sub>2</sub>O<sub>5</sub>)
  
== Isotopes ==
+
== Applications ==
29 [[radioisotope]]s of protactinium have been characterized, with the most stable being 231-Pa with a [[half life]] of 32760 years, 233-Pa with a half-life of 26.967 days, and 230-Pa with a half-life of 17.4 days. All of the remaining [[radioactive]] isotopes have half-lifes that are less than 1.6 days, and the majority of these have half lifes that are less than 1.8 seconds. This element also has 2 [[meta state]]s, 217m-Pa (t<sub>½</sub> 1.15 milliseconds) and 234m-Pa (t<sub>½</sub> 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 product]]s before 231-Pa are element Ac ([[actinium]]) isotopes and the primary products after are element U ([[uranium]]) isotopes.
+
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 ==
 
== Precautions ==
 +
 
Protactinium is both toxic and highly radioactive. It requires precautions similar to those used when handling [[plutonium]].
 
Protactinium is both toxic and highly radioactive. It requires precautions similar to those used when handling [[plutonium]].
 +
 +
== Notes ==
 +
<references />
  
 
==References==
 
==References==
<references />
+
 
 +
*[http://periodic.lanl.gov/elements/91.html "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. [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0 Online version].
 +
 
 +
* Cotton, F. Albert; and Wilkinson, Geoffrey (1980). ''Advanced Inorganic Chemistry'' (4th ed.), New York:Wiley. ISBN 0-471-02775-8.
 +
 
 +
*[http://www.webelements.com/webelements/elements/text/Pa/index.html Protactinium] WebElements.com. Retrieved March 10, 2007.
  
 
== External links ==
 
== External links ==
{{Commons|Protactinium}}
+
 
{{wiktionary|protactinium}}
+
* [http://www.webelements.com/webelements/elements/text/Pa/index.html Protactinium] WebElements.com.
* [http://www.webelements.com/webelements/elements/text/Pa/index.html WebElements.com - Protactinium]
+
* [http://education.jlab.org/itselemental/ele091.html Protactinium] It's Elemental.
* [http://education.jlab.org/itselemental/ele091.html It's Elemental - Protactinium]
+
* [http://pubs.acs.org/cen/80th/protactinium.html] InfoHaunter
* InfoHaunter [http://pubs.acs.org/cen/80th/protactinium.html]
 
  
 
[[Category:Physical sciences]]
 
[[Category:Physical sciences]]

Revision as of 06:25, 10 March 2007

91 thoriumprotactiniumuranium
Pr

Pa

(Uqu)
Pa-TableImage.png
periodic table
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
Main article: [[Isotopes of {{{isotopesof}}}]]
iso NA half-life DM DE (MeV) DP
230Pa syn 17.4 d ε 1.310 230Th
β- 0.563 230U
231Pa syn 32760 y α 5.149 227Ac
233Pa syn 26.967 d β- 0.571 233U

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 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, and shortened to Protactinium in 1949.

Aristid V. Grosse prepared 2 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 subsequently was sold to laboratories for a cost 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:

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

  1. Emsley, John (2001). Nature's Building Blocks, (Hardcover, First Edition), Oxford University Press, page 347. ISBN 0198503407. 

References
ISBN 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.

External links

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