Chem Explorers

Unveiling the Mysteries of Promethium: A Rare and Fascinating Element

Promethium: The Rare Earth Metal

Promethium is a rare and fascinating element that is part of the lanthanide series and was first discovered in the 1940s. Its discovery is attributed to Bohuslav Brauner, a Czech chemist, and his team, who were working at the Oak Ridge National Laboratory in Tennessee.

Origin of its Name

Promethium is named after Prometheus, the Greek mythological titan who stole fire from the gods and gave it to humanity. Similarly, Promethium is used primarily in nuclear batteries, and its unique properties make it an ideal energy source for remote and inaccessible locations where traditional batteries would not be practical.

Discovery of Promethium

Promethium was first discovered in 1945 by a team of scientists led by Bohuslav Brauner at the Oak Ridge National Laboratory in Tennessee. The researchers were isolating fission products from uranium that had been irradiated by neutrons.

Brauner’s team used ion-exchange chromatography to isolate a new element that appeared to have a unique spectrum. It was later confirmed to be Promethium, which was the last lanthanide element to be discovered.

Identification of Promethium

The atomic number of Promethium is 61, with a CAS number of 7440-12-2. It is a rare earth element and is part of the lanthanide series, which is also known as the rare earth metals.

Promethium is positioned in group 6 and period 6 of the periodic table. It has a relatively short half-life and decays into other isotopes through beta decay.

Properties and Characteristics of Promethium

Promethium is a radioactive rare earth metal with a chemical symbol of Pm and an atomic number of 61. It is one of the least abundant naturally occurring elements on Earth, with only about 500 grams thought to exist on the planet at any given time.

General Properties

Relative Atomic Mass and Atomic Mass

The relative atomic mass of Promethium is 145, and its atomic mass is 145 atomic mass units.

Physical Properties

Promethium is a dense, silvery-white metal that melts at 1,046 °C and boils at 3,000 °C. Its density is 7.26 g/cm3 at room temperature, which is higher than most other rare earth elements.

Promethium is a solid at room temperature, and it has a hardness of 2.5 Mohs.

Chemical Properties

Promethium has only one oxidation state, which is +3. It readily forms compounds with oxygen, fluorine, and other nonmetals.

The chemical properties of Promethium are similar to those of other rare earth elements, and it is usually prepared by reducing PmF3 with calcium in a vacuum.

Atomic Data of Promethium

Valence Electrons and Electron Configuration

Promethium has its outermost electrons in the 4f orbital and its electron configuration is [Xe] 4f5 6s2. This means that Promethium’s outermost electrons have a noble gas configuration.

Promethium has 5 valence electrons.

Quantum Numbers and Atomic Structure

Promethium has 61 electrons, 61 protons, and 84 neutrons. Its radius is approximately 183 picometers, and its first ionization energy is 540 kilojoules per mole.

Promethium has two stable isotopes, Pm-145 and Pm-147.

Uses of Promethium

Industrial Uses

Promethium has several industrial uses due to its radioactive decay. When Promethium-147 decays, it emits beta particles and gamma rays.

This radiation can be harnessed to produce phosphors for use in solar cells and other applications requiring light emission. Promethium-147 can also be used to measure the thickness of materials such as coatings on metal to determine its uniformity.

Additionally, Promethium can be used as a source of heat for thermoelectric generators.

Specific Uses

Promethium has several specific uses in various industries. For communication applications, it was once used in early radio receivers, and it played a part in the development of ultra-longwave wireless telegraphy in the early 1900s.

Promethium is also used in pacemakers as a source of ionizing radiation to stimulate a patient’s heart. In the military, Promethium is used in guided missiles to detect their velocity and location in space.

Interesting Facts about Promethium

Methods of Obtaining Promethium

Promethium can be obtained through several ways, including by-products of uranium fission and neutron bombardment. When uranium is fissioned in a nuclear reactor, small amounts of Promethium can be produced as a by-product.

Additionally, neutron bombardment of natural Nd-142 produces Pm-147 through beta decay.

Presence in the Andromeda Constellation

Promethium is the only element named after a mythological character that cannot be found on Earth in appreciable quantities. However, it can be detected in the spectra of some stars, including stars in the Andromeda constellation.

The presence of Promethium in stars is usually a result of the process of nucleosynthesis, whereby lighter elements combine to form heavier elements.

Cost of Promethium

Promethium is a relatively expensive element to produce because of its rarity and the difficulty in isolating it. The cost of Promethium is often measured in Curie, which is a unit of radioactive decay.

One Curie of Promethium-147 produces 3.7×10^10 decays per second, which means that the cost of Promethium is closely related to its radioactivity.

Despite its relatively high cost, Promethium has several unique uses that make it valuable.

Its radioactive decay can be harnessed in various industries, as discussed earlier in the article, and it also has applications in nuclear medicine, including radiation therapy.


Promethium is a fascinating element with unique properties and uses. Obtaining it can be difficult, and it is relatively expensive due to its rarity and radioactivity.

Nonetheless, Promethium has many applications in various fields, including nuclear medicine, military, and communication, among others. Its presence in stars, particularly in the Andromeda constellation, adds to its mystique, and further research into its properties may reveal more interesting facts about this rare earth metal.

In summary, Promethium is a rare and fascinating element that has unique physical and chemical properties. Its radioactivity makes it useful in various fields, including nuclear medicine, industrial, and military applications.

Obtaining Promethium is challenging, and its cost is related to its radioactivity. Despite its rarity and expense, Promethium is a valuable element with many practical uses.

In conclusion, Promethium’s unique properties and applications make it an important topic of study for scientists and industries alike.


  1. What is Promethium? Promethium is a rare earth element with an atomic number of 61.
  2. What are the properties of Promethium?
  3. Promethium has unique physical and chemical properties, including its radioactivity and beta decay.

  4. How is Promethium obtained?
  5. Promethium can be obtained by by-products of uranium fission or neutron bombardment.

  6. How is Promethium used?
  7. Promethium is used in various industries, including nuclear medicine, industrial, and military applications.

  8. What is the cost of Promethium?
  9. The cost of Promethium is related to its radioactivity and is typically measured in Curie.

  10. Is Promethium dangerous?
  11. Promethium is highly radioactive and can be dangerous to handle without proper precautions.

Popular Posts