Promethium
Definition and meaning of Promethium in chemistry.
Promethium is a chemical element with the symbol Pm and atomic number 61. It is a highly radioactive metal and holds the distinction of being the only lanthanide that lacks absolutely any stable isotopes. In nature, it occurs only in microscopic trace amounts as a spontaneous fission product in uranium ores.
In more detail
Promethium resides centrally in the f-block of the periodic table, situated directly between neodymium and samarium. Because of its intense instability, its chemical properties are far less extensively studied than those of other lanthanides, but it predominantly exists and reacts in the +3 oxidation state. Promethium salts exhibit a distinct pale pink or red color when dissolved in aqueous solutions. The element decays quite rapidly by releasing energetic beta particles, and its radioactivity is strong enough to cause the surrounding air to glow with a pale blue light in complete darkness. It is typically synthesized in nuclear reactors by the targeted neutron bombardment of neodymium or by chemically extracting it from the fission products of uranium fuel. Due to its intense radioactivity and extreme scarcity, promethium requires specialized handling protocols and heavy lead shielding.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Pm |
| Atomic number | 61 |
| Atomic mass | [145] u |
| Category | Lanthanide |
| State at room temperature | Solid |
| Melting point | 1042 °C |
| Year discovered | 1945 |
Promethium-147 is primarily used in compact atomic batteries to power highly specialized devices like deep-space spacecraft systems and medical pacemakers, as well as in luminous paint for instrument dials.
Frequently asked questions
Is promethium found naturally on Earth?
It exists on Earth only in extremely minute quantities, roughly 500 to 600 grams total across the entire crust, due solely to the natural fission of uranium.
How is promethium used in industrial thickness gauges?
Its reliable beta emissions are used to measure the exact thickness of materials like paper and plastics, as the physical material absorbs a highly predictable amount of radiation.