Actinides - List of Elements and Properties

List of Elements Belonging to the Actinide Group

The highlighted elements of this periodic table belong to the actinide element group.
The highlighted elements of this periodic table belong to the actinide element group. Todd Helmenstine

The actinide or actinoid elements are a series of elements including atomic number 89 (actinium) through 103 (lawrencium). Here is a list of elements that are actinides, a subset of the rare earth elements group. Discussions of actinide elements may refer to any member of the group by the symbol An. All of the elements are f-block elements, except sometimes actinium and lawrencium. As such, the actinides are a subset of the transition metals group.


  • The actinides are a subset of the transition metals. All of the elements are solid metals at room temperature.
  • The elements included in the actinide group run from actinium (atomic number 89) to lawrencium (atomic number 103).
  • All of the actinide elements are radioactive.
  • All of the actinides are f-block elements, except for lawrencium, which is a d-block element.

List of Actinide Elements

Here is a list of all of the elements in the actinide series:

Actinium (sometimes considered a transition metal yet not an actinide)
Lawrencium (sometimes considered a transition metal yet not an actinide)


The actinides are rare in nature, with only uranium and thorium found in more than trace amounts. So, they were discovered relatively recently compared with most other elements. Uranium, in the form of uranium oxide, was used in the Roman Empire. Martin Klaproth discovered the element in 1789, but it was not purified until 1841, by Eugène-Melchior Péligot. New elements were discovered, but researchers did not immediately realize they formed a family similar to the lanthanides. Instead, they were considered to be ordinary period 7 elements. Enrico Fermi predicted the presence of transuranium elements in 1943. In 1944, Glenn Seaborg proposed the "actinide hypothesis" to account for the unusual oxidation states of the elements. But, even in the late 1950s scientists didn't really recognize the difference between actinides and other metals.

Most of the actinides were discovered via synthesis, even though many occur naturally. Early on, scientists made actinides by bombarding uranium and plutonium with neutrons and other particles. Between 1962 and 1966, researchers focused on making new elements from nuclear explosions. Eventually, synthesis moved to the lab, where particle accelerators smashed atoms together and made new elements.

Actinide Properties

The actinides share several common properties with one another.

  • They are f-block elements, except for lawrencium.
  • All of the actinides are silver-colored radioactive metals. They have no stable isotopes.
  • Purified actinide metal is highly reactive and tarnishes easily.
  • The metals are dense and soft.
  • All of the actinides are paramagnetic.
  • Most of the elements have several crystal phases.
  • Most actinides are synthesized. Only uranium and thorium occur naturally in appreciable amounts.
  • For the most part, the actinides have properties similar to those of the lanthanides. Both groups of elements experience contraction moving across the periodic table. The ionic radius of the actinides decreases with increasing atomic number.
  • The actinides are pyrophoric. In other worse, they spontaneously ignite in air as finely divided powders.
  • Like the lanthanides, the actinides display several oxidation states. Usually, the most stable valence state is 3 or +4. Valence states between +3 and +7 are common.
  • These elements form numerous compounds.
  • All of the elements pose a health risk because of their radioactivity. Some are also toxic in their own right.
  • The actinides have several uses, mainly related to their radioactivity. Americium is used in smoke detectors. Thorium finds use in gas mantles. Most of the actinides have use in nuclear reactors and batteries. Some find use in nuclear weapons.


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Helmenstine, Anne Marie, Ph.D. "Actinides - List of Elements and Properties." ThoughtCo, Jan. 12, 2022, Helmenstine, Anne Marie, Ph.D. (2022, January 12). Actinides - List of Elements and Properties. Retrieved from Helmenstine, Anne Marie, Ph.D. "Actinides - List of Elements and Properties." ThoughtCo. (accessed January 19, 2022).