[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Astatine |
Symbol |
At |
| Atomic number |
85 |
Atomic weight |
(210) |
| Density @ 293 K |
? |
Atomic volume |
? |
| Group |
Halogen |
Discovered |
1940 |
| State (s, l, g) |
s |
| Melting point |
575.2 K |
Boiling point |
K |
| Heat of fusion |
? |
Heat of vaporization |
? |
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| 1st ionization energy |
890 kJ/mole |
Electronegativity |
2.2 |
| 2nd ionization energy |
kJ/mole |
Electron affinity |
270 kJ/mole |
| 3rd ionization energy |
kJ/mole |
Specific heat |
? |
| Heat atomization |
92 kJ/mole atoms |
| Shells |
2,8,18,32,18,7 |
Electron configuration |
[Xe] 4f14 5d10 6s2 6p5 |
| Minimum oxidation number |
-1 |
Maximum oxidation number |
7 |
| Minimumcommon oxidation number |
-1 |
Maximum common oxidation number |
1 |
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| Structure |
|
Color |
|
| Uses |
|
Toxicity |
|
| Hardness |
mohs |
Characteristics |
Radioactive |
| Reaction with air |
|
Reaction with 6M HCl |
|
| Reaction with 6M HCl |
|
Reaction with 15M HNO3 |
|
| Reaction with 6M NaOH |
|
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| Number of isotopes |
0 |
Hydride(s) |
HAt |
| Oxide(s) |
|
Chloride(s) |
|
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
pm |
Ionic radius (1+ ion) |
pm |
| Ionic radius (2+ ion) |
pm |
Ionic radius (3+ ion) |
pm |
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| Thermal conductivity |
J/m-sec-deg |
Electrical conductivity |
1/mohm-cm |
| Polarizability |
6 A^3 |
| Source |
Synthetic(Th or U decay) |
Rel. abund. solar system |
log |
| Abundance earth's crust |
log |
Cost, pure |
$/100g |
| Cost, bulk |
$/100g |
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History:
(Gr. astatos,
unstable) 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, with
naturally occurring uranium and thorium isotopes,
and traces of 217At are equilibrium with 233U and
239Np resulting from interation 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 in air. 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. Astatine is said to be more
metallic than 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.
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