|
95
Am
(243)
|
| Classification: | Americium is an actinide metal |
| Color: | silvery-white |
| Atomic weight: | (243), no stable isotopes |
| State: | solid |
| Melting point: | 1176 oC, 1449 K |
| Boiling point: | 2607 oC, 2880 K |
| Shells: | 2,8,18,32,25,8,2 |
| Electron configuration: | [Rn] 5f7 7s2 |
| Density @ 20oC: | 13.67 g/cm3 |
| Atomic volume: | 17.78 cm3/mol |
| Structure: | hcp: hexagonal close-packed |
| Hardness: | mohs |
Discovery of Americium
Americium was the fourth synthetic transuranium element of the actinide series to be discovered.
Americium-241 was first identified in 1944 by Seaborg, James and Morgan at the metallurgical laboratory at the University of Chicago. It was produced by the beta-particle decay of plutonium-241, which had been produced in a nuclear reactor by neutron bombardment of plutonium-239.
The researchers at first referred to americium as "pandemonium" owing to the difficulties they encountered trying to isolate it from another new element with which it was very closely associated, curium - or "delirium" as it was first called.
Americium was first isolated as a pure compound by Burris Cunningham in 1945.
The element was named after America, because it is located below Europium (element 63) in the periodic table, which was named after Europe.
Appearance & Characteristics
Americium-241 radiation emissions (preceded by Pitchblend ore ) displayed in a cloud chamber
The triangle in the glass tube contains the world's first sample of americium. (Photo credit: Berkeley Lab)
Harmful effects:
Americium is harmful due to its radioactivity.
Characteristics:
Americium is a silvery-white highly radioactive metal that has a density similar to lead.
It tarnishes slowly in dry air at room temperature.
Isotope 241Am, the most common isotope, decays to 237Np, emitting alpha and gamma radiation(1).
Isotope 241Am is used (in the form of americium dioxide) in very small amounts in 'ionization chamber' smoke detectors. One gram of americium dioxide provides enough active material for more than three million household smoke detectors(2).
Americium is used as a portable source of gamma rays and alpha particles for use in medicine, science and industry.
It is also used as a target material in nuclear research to make even heavier elements.
Americium is harmful due to its radioactivity.
Characteristics:
Americium is a silvery-white highly radioactive metal that has a density similar to lead.
It tarnishes slowly in dry air at room temperature.
Isotope 241Am, the most common isotope, decays to 237Np, emitting alpha and gamma radiation(1).
Uses of Americium
Isotope 241Am is used (in the form of americium dioxide) in very small amounts in 'ionization chamber' smoke detectors. One gram of americium dioxide provides enough active material for more than three million household smoke detectors(2).
Americium is used as a portable source of gamma rays and alpha particles for use in medicine, science and industry.
It is also used as a target material in nuclear research to make even heavier elements.
Abundance & Isotopes
Abundance earth's crust: nil
Abundance solar system: negligible
Cost, pure: $1500 per g
Cost, bulk: per 100g
Source: Americium is obtained as a by-product of plutonium processing.
Isotopes: Americium has 14 isotopes whose half-lives are known, with mass numbers 232 to 247. Americium has no naturally occuring isotopes. Its longest lived isotopes are 243Am, with a half-life of 7370 years, 241Am with a half-life of 432.2 years and 242Am with a half-life of 141 years.
Abundance solar system: negligible
Cost, pure: $1500 per g
Cost, bulk: per 100g
Source: Americium is obtained as a by-product of plutonium processing.
Isotopes: Americium has 14 isotopes whose half-lives are known, with mass numbers 232 to 247. Americium has no naturally occuring isotopes. Its longest lived isotopes are 243Am, with a half-life of 7370 years, 241Am with a half-life of 432.2 years and 242Am with a half-life of 141 years.
Energies
Specific heat capacity: 0.11 J g-1 K-1
Heat of fusion: 14.40 kJ mol-1
1st ionization energy: 578 kJ mol-1
3rd ionization energy: kJ mol-1
Heat of fusion: 14.40 kJ mol-1
1st ionization energy: 578 kJ mol-1
3rd ionization energy: kJ mol-1
Heat of atomization: 266 kJ mol-1
Heat of vaporization: 238.5 kJ mol-1
2nd ionization energy: kJ mol-1
Electron affinity: kJ mol-1
Heat of vaporization: 238.5 kJ mol-1
2nd ionization energy: kJ mol-1
Electron affinity: kJ mol-1
Oxidation & Electrons
Shells: 2,8,18,32,25,8,2
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.3
Minimum oxidation number: 0
Min. common oxidation no.: 0
Electronegativity (Pauling Scale): 1.3
Electron configuration: [Rn] 5f7 7s2
Maximum oxidation number: 6
Max. common oxidation no.: 3
Polarizability volume: 23.3 Å3
Maximum oxidation number: 6
Max. common oxidation no.: 3
Polarizability volume: 23.3 Å3
Reactions & Compounds
Reaction with air:
Reaction with 15 M HNO3:
Oxide(s): AmO, AmO2, Am2O3
Hydride(s): AmH2 AmH3
Reaction with 15 M HNO3:
Oxide(s): AmO, AmO2, Am2O3
Hydride(s): AmH2 AmH3
Reaction with 6 M HCl:
Reaction with 6 M NaOH:
Chloride(s): AmCl2, AmCl3
Reaction with 6 M NaOH:
Chloride(s): AmCl2, AmCl3
Radius
Atomic radius: 173 pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (2+ ion): pm
Ionic radius (2- ion): pm
Ionic radius (1+ ion): pm
Ionic radius (3+ ion): 111.5 pm
Ionic radius (1- ion): pm
Ionic radius (3+ ion): 111.5 pm
Ionic radius (1- ion): pm
Conductivity
Thermal conductivity: 10 W m-1 K-1
Electrical conductivity: 0.7 x 106 S m-1
References
1. James D. Navratil, Wallace W. Schulz, Glenn T. Seaborg., The Most Useful Actinide Isotope: Americium-241., Journal of Chemical Education. 67.1 (1990): p15-16.
2. Smoke Detectors and Americium., World Nuclear Association.
2. Smoke Detectors and Americium., World Nuclear Association.
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