[General | States | Energies | Oxidation & Electrons]
[Appearance & Characteristics | Reactions | Other Forms]
[Radius | Conductivity
| Abundance | History]
| Name |
Americium |
Symbol |
Am |
| Atomic number |
95 |
Atomic weight |
(243) |
| Density @ 293 K |
13.6 g/cm3 |
Atomic volume |
17.86 cm3/mol |
| Group |
Rare Earth, Actinides |
Discovered |
1944 |
| State (s, l, g) |
s |
| Melting point |
1267.2 K |
Boiling point |
2873 K |
| Heat of fusion |
14.40 kJ/mol |
Heat of vaporization |
? |
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| 1st ionization energy |
578 kJ/mole |
electronegativity |
1.3 |
| 2nd ionization energy |
kJ/mole |
Electron affinity |
kJ/mole |
| 3rd ionization energy |
kJ/mole |
Specific heat |
0.11 J/gK |
| Heat atomization |
kJ/mole atoms |
| Shells |
2,8,18,32,25,8,2 |
Electron configuration |
[Rn] 5f7 7s2 |
| Minimum oxidation number |
0 |
Maximum oxidation number |
6 |
| Minimum common oxidation number |
0 |
Maximum common oxidation number |
3 |
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| Structure |
fcc: face-centered cubic |
Color |
silvery-white |
| Uses |
smoke detector |
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) |
AmH2 AmH3 |
| Oxide(s) |
AmO Am2O3 AmO2 |
Chloride(s) |
AmCl2 AmCl3 |
| Ionic radius (2- ion) |
pm |
Ionic radius (1- ion) |
pm |
| Atomic radius |
173 pm |
Ionic radius (1+ ion) |
pm |
| Ionic radius (2+ ion) |
pm |
Ionic radius (3+ ion) |
111.5 pm |
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| Thermal conductivity |
J/m-sec-deg |
Electrical conductivity |
1/mohm-cm |
| Polarizability |
23.3 A^3 |
| Source |
Synthetic |
Rel. abund. solar system |
log |
| Abundance earth's crust |
log |
Cost, pure |
$/100g |
| Cost, bulk |
$/100g |
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History:
(the Americas)
Americium was the fourth transuranic element to
be discovered; the isotope 241Am was identified
by Seaborg, James, Morgan, and Ghiorso late in
1944 at the wartime Metallurgical Laboratory of
the University of Chicago as the result of
successive neutron capture reactions by plutonium
isotopes in a nuclear reactor. The luster of
freshly prepared americium metal is white and
more silvery than plutonium or neptunium prepared
in the same manner. It appears to be more
malleable than uranium or neptunium and tarnishes
slowly in dry air at room temperature. Americium
must be handled with great care to avoid personal
contamination. The alpha activity from 241Am is
about three times that of radium. When gram
quantities of 241Am are handled, the intense
gamma activity makes exposure a serious problem.
241Am has been used as a portable source for
gamma radiography. It has also been used as a
radioactive glass thickness gage for the flat
glass industry and as a source of ionization for
smoke detectors.
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