Americium

Americium,  ₉₅Am

General properties
Name, symbol	Americium, Am
Appearance	Silvery-gray
Americium in the periodic table
Eu ↑ Am ↓ - Plutonium ← Americium → Curium
Atomic number	95
Standard atomic weight (Ar)	243
Group, block	, f-block
Period	period 7
Electron configuration	[Rn] 5f7 7s2
per shell	2, 8, 18, 32, 25, 8, 2
Physical properties
Silvery-grey
Phase	Solid
Melting point	1449 K ​(1176 °C, ​2149 °F)
Density near r.t.	12 g/cm3
Heat of fusion	14.39 kJ/mol
Molar heat capacity	62.7 J/(mol·K)
pressure
Atomic properties
Oxidation states	8, 7, 6, 5, 4, 3, 2 ​(an amphoteric oxide)
Electronegativity	Pauling scale: 1.3
energies	1st: 578 kJ/mol
Atomic radius	empirical: 173 pm
Covalent radius	180±6 pm
Miscellanea
Crystal structure	​Double hexagonal close-packed (dhcp)
Thermal conductivity	10 W/(m·K)
Electrical resistivity	0.69 Ω·m
Magnetic ordering	Paramagnetic
CAS Registry Number	7440-35-9
History
Naming	After the Americas
Discovery	Glenn T. Seaborg, Ralph A. James, Leon O. Morgan, Albert Ghiorso (1944)

Americium is a radioactive chemical element, a transuranic member of the actinide series, with symbol Am and atomic number 95. The most important isotope of this element is Americium-241 (²⁴¹Am).

Properties

Chemical

Like all actinides, americium reacts with air and halogens at standard conditions.

Physical

Americium is a silvery-gray metal, with a density of 12 g/cm³ at room temperature. It melts at 1176 °C and boils at 2607 °C.

Availability

Americium is readily found in smoke detectors, in the form of americium dioxide aggregate deposited on a small Al button, which is the ionization source for the smoke detector. Each radioactive button contains around 0.26 micrograms of ²⁴¹Am. To obtain a significant amount of Am, you will need dozens (minimum) of Am buttons. However, acquiring lots of smoke detectors may draw the attention of the authorities.

Isolation

Isolation of this element is difficult to do given the low concentration of Am in smoke detectors and its high reactivity.

Projects

• Make your own personalized smoke detector
• Neutron source
• Make a spectometer

Handling

Safety

Americium, like all actinides, is radioactive and very toxic, but the amounts encountered in smoke detector buttons are too small to pose any appreciable hazard.

Storage

Americium should be kept in thick vials, lead is also good for shielding.

Disposal

Americium should be taken to centers that take care of used smoke detectors.

References

Relevant Sciencemadness threads

• How much Americium-241 contains in a fire detector?
• Simple Americium 241 Experiments?
• Will americium dissolve in acid?
• Am241 beads