Introduction
Group: 17 or VII A
Atomic Weight: 210
Period: 6
CAS Number: 7440-68-8
Classification
No Stable Isotopes
Solid
Liquid
Gas
Solid (Predicted)
Description • Uses/Function
Synthesized in 1940 by D. R. Corson, K. R. MacKenzie, and E. Segre at the University of California by bombarding bismuth with alpha particles. The longest-lived isotopes, 210At, have a half-life of only 8.1 hours. Thirty-four isotopes and isomers are now known. Minute quantities of 215At, 218At, and 219At exist in equilibrium in nature with naturally occurring uranium and thorium isotopes, and traces of 217At are equilibrium with 233U and 239Np resulting from interaction of thorium and uranium with naturally produced neutrons. The total amount of astatine present in the earth’s crust, however, is less than 1 oz. Astatine can be produced by bombarding bismuth with energetic alpha particles to obtain the relatively long-lived 209–211At, which can be distilled from the target by heating it in air. Only about 0.05 mg of astatine has been prepared to date. The “time of flight” mass spectrometer has been used to confirm that this highly radioactive halogen behaves chemically very much like other halogens, particularly iodine. The interhalogen compounds AtI, AtBr, and AtCl are known to form, but it is not yet known if astatine forms diatomic astatine molecules. HAt and CH3At (methyl astatide) have been detected. Astatine is said to be more metallic that iodine, and, like iodine, it probably accumulates in the thyroid gland. Workers at the Brookhaven National Laboratory have recently used reactive scattering in crossed molecular beams to identify and measure elementary reactions involving astatine. 1
Physical Properties
Melting Point:2* 302 °C = 575.15 K = 575.6 °F
Electron Configuration: [Xe] 6s2 4f14 5d10 6p5
n = 6
Electronegativity (Pauling scale):3 2.2
Specific Heat:
External Links:
(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:4-4:5.
Boiling Point:2*
Sublimation Point:2
Triple Point:2
Critical Point:2
Density: g/cm3
* - at 1 atm
Electron Configuration
Block: p
Highest Occupied Energy Level: 6
Valence Electrons: 7
Quantum Numbers:
ℓ = 1
mℓ = 0
ms = -½
Bonding
Electropositivity (Pauling scale): 1.8
Electron Affinity:4 2.8 eV
Oxidation States:
Thermochemistry
Thermal Conductivity: 1.7 (W/m)/K, 27°C 5
Heat of Fusion:
Heat of Vaporization:
State of Matter
Enthalpy of Formation (ΔHf°)6
Entropy (S°)6
Gibbs Free Energy (ΔGf°)6
(kcal/mol)
(kJ/mol)
(cal/K)
(J/K)
(kcal/mol)
(kJ/mol)
(s)
0
0
29.0
121.336
0
0
Isotopes
Nuclide
Mass 7
Half-Life 7
Nuclear Spin 7
Binding Energy
191At
1.7(+11-5) ms
(1/2+)
193At
192.99984(6)
28(+5-4) ms
(1/2+)
1,500.58 MeV
194At
193.99873(20)
~40 ms
3+#
1,508.65 MeV
195At
194.996268(10)
328(20) ms
(1/2+)
1,516.72 MeV
196At
195.99579(6)
253(9) ms
3+#
1,524.79 MeV
197At
196.99319(5)
0.390(16) s
(9/2-)
1,532.86 MeV
198At
197.99284(5)
4.2(3) s
(3+)
1,540.93 MeV
199At
198.99053(5)
6.92(13) s
(9/2-)
1,549.01 MeV
200At
199.990351(26)
43.2(9) s
(3+)
1,557.08 MeV
201At
200.988417(9)
85(3) s
(9/2-)
1,574.46 MeV
202At
201.98863(3)
184(1) s
(2,3)+
1,582.53 MeV
203At
202.986942(13)
7.37(13) min
9/2-
1,590.61 MeV
204At
203.987251(26)
9.2(2) min
7+
1,598.68 MeV
205At
204.986074(16)
26.2(5) min
9/2-
1,606.75 MeV
206At
205.986667(22)
30.6(13) min
(5)+
1,614.82 MeV
207At
206.985784(23)
1.80(4) h
9/2-
1,622.89 MeV
208At
207.986590(28)
1.63(3) h
6+
1,630.96 MeV
209At
208.986173(8)
5.41(5) h
9/2-
1,639.03 MeV
210At
209.987148(8)
8.1(4) h
(5)+
1,647.10 MeV
211At
210.9874963(30)
7.214(7) h
9/2-
1,655.18 MeV
212At
211.990745(8)
0.314(2) s
(1-)
1,653.93 MeV
213At
212.992937(5)
125(6) ns
9/2-
1,662.00 MeV
214At
213.996372(5)
558(10) ns
1-
1,670.07 MeV
215At
214.998653(7)
0.10(2) ms
9/2-
1,678.15 MeV
216At
216.002423(4)
0.30(3) ms
1-
1,676.90 MeV
217At
217.004719(5)
32.3(4) ms
9/2-
1,684.97 MeV
218At
218.008694(12)
1.5(3) s
1-#
1,693.05 MeV
219At
219.011162(4)
56(3) s
5/2-#
1,691.80 MeV
220At
220.01541(6)
3.71(4) min
3(-#)
1,699.87 MeV
221At
221.01805(21)#
2.3(2) min
3/2-#
1,707.94 MeV
222At
222.02233(32)#
54(10) s
1,706.70 MeV
223At
223.02519(43)#
50(7) s
3/2-#
1,714.77 MeV
Values marked # are not purely derived from experimental data, but at least partly from systematic trends. Spins with weak assignment arguments are enclosed in parentheses. 7
Abundance
Safety Information
Material Safety Data Sheet - ACI Alloys, Inc.
For More Information
American Elements
Chemical & Engineering News
Chemical Elements
ChemGlobe
Chemicool
Environmental Chemistry
Sources
(2) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:132.
(3) - Lide, David R. CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, 2002; p 10:147-10:148.
(4) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:193, 12:219-220.
(5) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:123-6:137.
(6) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; pp 6:107-6:122.
(7) - Dean, John A. Lange's Handbook of Chemistry, 12th ed.; McGraw-Hill Book Company: New York, NY, 1979; p 9:4-9:94.
(8) - Atomic Mass Data Center. http://amdc.in2p3.fr/web/nubase_en.html (accessed July 14, 2009).