Promethium

Promethium,  ₆₁Pm

General properties
Name, symbol	Promethium, Pm
Pronunciation	/proʊˈmiːθiəm/ (proh-MEE-thee-əm)
Appearance	Metallic, silvery, glowing
Promethium in the periodic table
- ↑ Pm ↓ Np Neodymium ← Promethium → Samarium
Atomic number	61
Standard atomic weight (Ar)
Group, block	n/a; f-block
Period	period 6
Electron configuration	[Xe] 4f5 6s2
per shell	2, 8, 18, 23, 8, 2
Physical properties
Phase	Solid
Melting point	1315 K ​(1042 °C, ​1908 °F)
Boiling point	3273 K ​(3000 °C, ​5432 °F)
Density near r.t.	7.26 g/cm3
Heat of fusion	7.13 kJ/mol
Heat of	289 kJ/mol
Atomic properties
Oxidation states	+2, +3
energies	1st: 540 kJ/mol 2nd: 1050 kJ/mol 3rd: 2150 kJ/mol
Atomic radius	empirical: 183 pm
Covalent radius	199 pm
Miscellanea
Crystal structure	​
Thermal expansion	9.0 µm/(m·K) (at room temperature)
Thermal conductivity	17.9 W/(m·K)
Electrical resistivity	0.75 Ω·m (at 20 °C) (estimated)
Magnetic ordering	paramagnetic
Young's modulus	α form: est. 46 GPa
Shear modulus	α form: est. 18 GPa
Bulk modulus	α form: est. 33 GPa
Poisson ratio	α form: est. 0.28 GPa
CAS Registry Number	7440-12-2
History
Discovery	Chien Shiung Wu, Emilio Segrè, Hans Bethe (1942)
First isolation	Charles D. Coryell, Jacob A. Marinsky, Lawrence E. Glendenin (1945)
Named by	Grace Mary Coryell (1945)

Promethium (Pm) is an extremely radioactive lanthanide. It is one of two classical elements lighter than bismuth, with no stable isotopes, the other being technetium. It is not encountered in nature except for traces and is primarily synthesized in labs.

Properties

Chemical

The chemistry of promethium is very similar to that of other lanthanides.

Physical

Promethium is a silvery-gray metal, which glows in dark. It readily oxidizes in air.

The most stable isotope of the element is promethium-145, which has a specific activity of 940 Ci/g (35 TBq/g) and a half-life of 17.7 years via electron capture.

Availability

Promethium is extremely hard to find, but some sellers do exist. It's very expensive.

Isolation

While it's possible to reduce promethium from the fluorescent dye it's commonly available, one would need a very large amount of Pm dye, large enough that its radioactivity becomes a serious hazard. As such, it's not a good idea to isolate this metal, unless one has the setting to do this safely.

In industry, promethium is synthesized by bombarding uranium-235 (enriched uranium) with thermal neutrons to produce promethium-147 as a fission product. Pm-145, the more stable isotope, can be produced via the radioactive decay of samarium-145.

Projects

• Element collection
• Study radioactivity
• Luminous paint
• Atomic batteries

Handling

Safety

Promethium is highly radioactive and proper protection should be worn when handling the compound.

Storage

In closed vials, kept in lead-lined boxes.

Disposal

To do

References

Relevant Sciencemadness threads

• Why technetium and promethium doesn't have a stable isotope?