Difference between revisions of "Astatine" - New World Encyclopedia

Vapor pressure
85	polonium ← astatine → radon
	periodic table
General
Name, Symbol, Number	astatine, At, 85
Chemical series	halogens
Group, Period, Block	17, 6, p
Appearance	metallic (presumed)
Atomic mass	(210) g/mol
Electron configuration	[Xe] 4f14 5d10 6s2 6p5
Electrons per shell	2, 8, 18, 32, 18, 7
Physical properties
Phase	solid
Melting point	575 K; (302 °C, 576 °F)
Boiling point	? 610 K; (? 337 °C, ? 639 °F)
Heat of vaporization	ca. 40 kJ/mol
Atomic properties
Crystal structure	no data
Oxidation states	±1, 3, 5, 7
Electronegativity	2.2 (Pauling scale)
Ionization energies	1st: (est.) 920 kJ/mol
Miscellaneous
Magnetic ordering	no data
Thermal conductivity	(300 K) 1.7 W/(m·K)
CAS registry number	7440-68-8
Notable isotopes

Latest revision as of 05:08, 18 August 2023

Astatine (chemical symbol At, atomic number 85) is the rarest naturally occurring chemical element. It is a member of the halogen family of elements and is the heaviest halogen. Its chemical properties appear to resemble those of iodine. All its isotopes are radioactive, and a few of them are produced by the natural radioactive decay of uranium-235 and uranium-238. Various compounds of astatine have been prepared in minute amounts, and the possibility of their use for nuclear medicine is being studied.

Occurrence and production

The total amount of astatine in the Earth's crust has been estimated to be less than one ounce (28 grams) at any given time—corresponding to no more than one teaspoonful in volume. It is produced in nature by the radioactive decay of uranium and thorium, and it is therefore present in trace amounts in minerals of these elements.

Astatine can be artificially produced by bombarding bismuth with energetic alpha particles. This method generates the relatively long-lived isotopes ²⁰⁹At, ²¹⁰At, and ²¹¹At. These isotopes can then be separated from the bismuth by a process of distillation, which involves heating the mixture in the presence of air, and condensing the vapors in a separate container.

History

The name astatine was derived from the Greek word αστατος (astatos), meaning "unsteady." Long before it was discovered, Dmitri Mendeleev had predicted its existence based on his analysis of the periodic table. He called it "eka-iodine."

This element was discovered in 1940 by Dale R. Corson, K. R. MacKenzie, and Emilio Segrè at the University of California, Berkeley. They found it during experiments in which they subjected bismuth to a barrage of alpha particles. An earlier name for the element was alabamine (Ab).

Notable characteristics

In the periodic table, astatine is located in group 17 (former group 7A), the halogen family, below iodine. In addition, it lies in period six, between polonium and radon.

According to experiments done with a mass spectrometer, the chemical properties of this highly radioactive element probably resemble those of the other halogens, especially iodine. (Like iodine, it would be expected to accumulate in the thyroid gland.) Yet astatine is thought to be more metallic than iodine and is classified as a metalloid. Researchers at the Brookhaven National Laboratory have been able to study elementary reactions that involve astatine, but chemical research into this element is limited by its extreme rarity, which is a result of its extremely short half-life.

Isotopes

Astatine has many known isotopes, all of which are radioactive. Their mass numbers range from 191 to 223. There exist also 23 metastable excited states. Among the various known isotopes, the longest-lived member is ²¹⁰At, which has a half-life of 8.1 hours; the shortest-lived member is ²¹³At, which has a half-life of 125 nanoseconds.

Compounds

Multiple compounds of astatine have been synthesized in microscopic amounts and studied as intensively as possible before their inevitable radioactive disintegration. These compounds are primarily of theoretical interest. They are, however, also being studied for their potential use in nuclear medicine.

References
ISBN links support NWE through referral fees

Astatine Los Alamos National Laboratory. Retrieved October 3, 2007.
Cotton, F. Albert, and Geoffrey Wilkinson. Advanced Inorganic Chemistry, 4th ed. New York: Wiley, 1980. ISBN 0-471-02775-8
Chang, Raymond. Chemistry, ninth ed. New York: McGraw-Hill Science/Engineering/Math, 2006. ISBN 0073221031
Greenwood, N.N., and A. Earnshaw. Chemistry of the Elements, 2nd Edition. Oxford, U.K.; Burlington, Massachusetts: Butterworth-Heinemann, Elsevier Science, 1998. ISBN 0750633654 Online Version Retrieved October 3, 2007.

External links

All links retrieved August 18, 2023.

WebElements.com - Astatine

Credits

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History of "Astatine"

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@@ Line 1: / Line 1: @@
+{{Copyedited}}{{Images OK}}{{Submitted}}{{Approved}}{{Paid}}
 {{Elementbox_header | number=85 | symbol=At | name=astatine | left=[[polonium]] | right=[[radon]] | above=[[iodine|I]] | below=([[Uus]]) | color1=#ffff99 | color2=purple }}
 {{Elementbox_series | [[halogen]]s }}
@@ Line 29: / Line 30: @@
 {{Elementbox_footer | color1=#ffff99 | color2=black }}
-'''Astatine''' (chemical symbol '''At''', [[atomic number]] 85) is a [[radioactive]] element that occurs naturally from [[uranium]]-235 and [[uranium]]-238 decay. It is the heaviest of the [[halogen]]s.
+'''Astatine''' (chemical symbol '''At''', [[atom|atomic number]] 85) is the rarest naturally occurring [[chemical element]]. It is a member of the [[halogen]] family of elements and is the heaviest halogen. Its chemical properties appear to resemble those of [[iodine]]. All its [[isotope]]s are [[radioactive]], and a few of them are produced by the natural radioactive decay of [[uranium]]-235 and uranium-238. Various compounds of astatine have been prepared in minute amounts, and the possibility of their use for nuclear medicine is being studied.
+{{toc}}
+== Occurrence and production ==
-== Occurrence and production ==
+The total amount of astatine in the [[Earth]]'s crust has been estimated to be less than one ounce (28 grams) at any given time&mdash;corresponding to no more than one teaspoonful in volume. It is produced in nature by the [[radioactive decay]] of [[uranium]] and [[thorium]], and it is therefore present in trace amounts in [[mineral]]s of these elements.
-Astatine is produced by bombarding [[bismuth]] with energetic [[alpha particles]] to obtain the relatively long-lived isotopes <sup>209</sup>At, <sup>210</sup>At, and <sup>211</sup>At. These isotopes  can then be separated from the bismuth by a process of [[distillation]], which involves heating in the presence of air.
+Astatine can be artificially produced by bombarding [[bismuth]] with energetic [[alpha particles]]. This method generates the relatively long-lived isotopes <sup>209</sup>At, <sup>210</sup>At, and <sup>211</sup>At. These isotopes can then be separated from the bismuth by a process of [[distillation]], which involves heating the mixture in the presence of [[air]], and condensing the vapors in a separate container.
 == History ==
-The existence of "eka-iodine" had been predicted by [[Mendeleev]]. Astatine (after [[Greek language|Greek]] αστατος ''astatos'', meaning "unsteady") was first synthesized in [[1940]] by [[Dale R. Corson]], [[K. R. MacKenzie]], and [[Emilio Segrè]] at the [[University of California, Berkeley]] by barraging [[bismuth]] with [[alpha particle]]s. An earlier name for the element was ''alabamine'' (Ab).
+The name astatine was derived from the [[Greek language|Greek]] word αστατος ''(astatos)'', meaning "unsteady." Long before it was discovered, [[Dmitri Mendeleev]] had predicted its existence based on his analysis of the [[periodic table]]. He called it "eka-iodine."
+This element was discovered in 1940 by [[Dale R. Corson]], [[K. R. MacKenzie]], and [[Emilio Segrè]] at the [[University of California, Berkeley]]. They found it during experiments in which they subjected [[bismuth]] to a barrage of [[alpha particle]]s. An earlier name for the element was ''alabamine'' (Ab).
 == Notable characteristics ==
-This highly [[radioactive]] element has been confirmed by [[mass spectrometer]]s to behave chemically much like other [[halogen]]s, especially [[iodine]] (it would probably accumulate in the [[thyroid]] gland like iodine). Astatine is thought to be more [[metal]]lic than iodine.  Researchers at the [[Brookhaven National Laboratory]] have performed experiments that have identified and measured elementary reactions that involve astatine; however, chemical research into astatine is limited by its extreme rarity, which is a result of its extremely short [[half-life]].
-Astatine is the rarest naturally-occurring element, with the total amount in Earth's crust estimated to be less than 1 [[ounce|oz]] (28 g) at any given time; this amounts to less than one teaspoon of the element. The [[Guinness Book of Records]] has dubbed the element the rarest on Earth, stating: "Only around 0.9 oz (25 [[gram|g]]) of the element astatine (At) occurring naturally"; [[Isaac Asimov]] wrote a 1955 essay on [[large numbers]], [[scientific notation]], and the size of the atom, in which he stated that the number of astatine atoms on Earth at any time was "only a [[trillion]]".
+In the [[periodic table]], astatine is located in group 17 (former group 7A), the halogen family, below [[iodine]]. In addition, it lies in period six, between [[polonium]] and [[radon]].
+According to experiments done with a [[mass spectrometer]], the chemical properties of this highly [[radioactive]] element probably resemble those of the other [[halogen]]s, especially [[iodine]]. (Like iodine, it would be expected to accumulate in the [[thyroid]] gland.) Yet astatine is thought to be more [[metal]]lic than iodine and is classified as a [[metalloid]]. Researchers at the [[Brookhaven National Laboratory]] have been able to study elementary reactions that involve astatine, but chemical research into this element is limited by its extreme rarity, which is a result of its extremely short [[half-life]].
 === Isotopes ===
-Astatine has many known [[isotope]]s, all of which are [[radioactive]]. Their mass numbers range from 191 to 223. There exist also 23 [[metastable]]* [[excited state]]*s. Among the various known isotopes, the longest-lived member is <sup>210</sup>At, which has a [[half-life]]* of 8.1 hours; the shortest-lived member is <sup>213</sup>At, which has a half-life of 125 [[nanoseconds]]*.
+Astatine has many known [[isotope]]s, all of which are [[radioactive]]. Their mass numbers range from 191 to 223. There exist also 23 [[metastable]] [[excited state]]s. Among the various known isotopes, the longest-lived member is <sup>210</sup>At, which has a [[half-life]] of 8.1 hours; the shortest-lived member is <sup>213</sup>At, which has a half-life of 125 [[nanoseconds]].
 == Compounds ==
-Multiple [[chemical compound|compounds]] of astatine have been synthesized in microscopic amounts and studied as intensively as possible before their inevitable radioactive disintegration. These compounds are primarily of theoretical interest; however, they are also being studied for potential use in [[nuclear medicine]].
+Multiple [[chemical compound|compounds]] of astatine have been synthesized in microscopic amounts and studied as intensively as possible before their inevitable radioactive disintegration. These compounds are primarily of theoretical interest. They are, however, also being studied for their potential use in [[nuclear medicine]].
 == See also ==
@@ Line 54: / Line 62: @@
 * [[Chemical element]]
 * [[Halogen]]
+* [[Iodine]]
 * [[Periodic table]]
 == References ==
-*[http://periodic.lanl.gov/elements/85.html Astatine] Los Alamos National Laboratory. Accessed on December 10, 2006.
+*[http://periodic.lanl.gov/elements/85.html Astatine] Los Alamos National Laboratory. Retrieved October 3, 2007.
-* 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 available at [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0]. Accessed on November 5, 2006.
+* Cotton, F. Albert, and Geoffrey Wilkinson. ''Advanced Inorganic Chemistry'', 4th ed. New York: Wiley, 1980. ISBN 0-471-02775-8
-* Cotton, F. Albert; and Wilkinson, Geoffrey (1980), ''Advanced Inorganic Chemistry'' (4th ed.), New York: Wiley. ISBN 0-471-02775-8.
+* Chang, Raymond. ''Chemistry'', ninth ed. New York: McGraw-Hill Science/Engineering/Math, 2006. ISBN 0073221031
-* Chang, Raymond (2006). ''Chemistry'' (ninth ed.) New York: McGraw-Hill Science/Engineering/Math. ISBN 0073221031.
+* Greenwood, N.N., and A. Earnshaw. ''Chemistry of the Elements'', 2nd Edition. Oxford, U.K.; Burlington, Massachusetts: Butterworth-Heinemann, Elsevier Science, 1998. ISBN 0750633654 [http://www.knovel.com/knovel2/Toc.jsp?BookID=402&VerticalID=0 Online Version] Retrieved October 3, 2007.
 == External links ==
+All links retrieved August 18, 2023.
 *[http://www.webelements.com/webelements/elements/text/At/index.html WebElements.com - Astatine]
 [[Category:Physical sciences]]