Actinium

The actinium is a chemical element that is classified as an actinide metal. It was discovered in 1899 by André Debierne.

Discovery of actinium

The radioactive element actinium was discovered by Andre Debierne in 1899 in Paris, France.

Debierne worked with Marie Curie and discovered actinium in pitchblende (uranium ore) from which radium and polonium had already been extracted. He was able to identify the presence of a new element because the radioactive emission profile of his sample could not be explained by the presence of any known element.

Debierne was unable to isolate pure actinium from thorium also present in pitchblende.

Appearance and Characteristics

Harmful effects:

  • Actinium is highly radioactive.

Characteristics:

  • Actinium is radioactive; glows in the dark.

Uses of actinium

Actinium is used as a neutron source.

Abundance and isotopes

  • Abundance in the earth’s crust: 0.0005 parts per trillion by weight.
  • Abundance in the solar system: insignificant
  • Source: Natural radioactive decay of U-235. One ton of pitchblende contains about 0.15 milligrams of actinium. Today, actinium is generally produced by irradiation of 226Ra neutrons.
  • Isotopes: Actinium has 29 isotopes. All are radioactive. 227Ac occurs naturally in uranium ore and, at 21,773 years, has the longest Ac half-life.
Symbol Ac
Atomic Number 89
Valence +3
Atomic weight 227
Boiling point (ºC) 3198 
Melting point (ºC) 1050 
Density (Kg/m3) 10070
Atomic structure [Rn] 6d1 7s2

Discover more elements in our periodic table.