ASTATINE

Introduction

Atomic Number: 85
Group: 17 or VII A
Atomic Weight: 210
Period: 6
CAS Number: 7440-68-8

Classification

Chalcogen
Halogen
Noble Gas
Lanthanoid
Actinoid
Rare Earth Element
Platinum Group Metal
Transuranium
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
Boiling Point:2
Sublimation Point:2 
Triple Point:2 
Critical Point:2 
Density:   g/cm3

* - at 1 atm

Electron Configuration

Electron Configuration: [Xe] 6s2 4f14 5d10 6p5
Block: p
Highest Occupied Energy Level: 6
Valence Electrons: 7

Quantum Numbers:

n = 6
ℓ = 1
m = 0
ms = -½

Bonding

Electronegativity (Pauling scale):3 2.2
Electropositivity (Pauling scale): 1.8
Electron Affinity:4 2.8 eV
Oxidation States: 

Thermochemistry

Specific Heat: 
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

External Links:

Sources

(1) - Lide, David R. CRC Handbook of Chemistry and Physics, 83rd ed.; CRC Press: Boca Raton, FL, 2002; p 4:4-4:5.
(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).