|Atomic Symbol||Atomic symbol::Ac|
|Atomic Number||Atomic number::89|
|Atomic Weight||Atomic weight::227.0278 g/mol|
|Group, Period, Block||IIIB, 7, f|
|Electron configuration||[Rn] 6d1, 7s2|
|Electrons per shell|| 2,8,18,32,18,9,2|
|CAS number||CAS number::7440-34-8|
|Melting point||Melting point::1050° C|
|Boiling point||Boiling point::3199° C|
|Isotopes of Actinium|
|All properties are for STP unless otherwise stated.|
Actinium is a chemical element that is classified as a transition metal and the first element in the actinide series. Discovered in 1899 by André-Louis Debierne, it was named actinium for the Greek word for beam, aktis. On the Periodic table, it is located in Group IIIB and period 7.It is among the f block of elements, meaning that all of its valence electrons are in the f sublevel. As a transition metal, it bears metallic properties that vary widely from other transition metals. It is only found in trace amounts in samples of uranium ore. Like many larger elements, it is highly radioactive and can be hazardous for one's health. Its longest lasting isotope, 227Ac, has a half life of 21.773 years. This is relatively short amongst normal elements, but very long among elements with higher atomic mass. 
Actinium, while only existing in small quantities, has several measurable properties.It exists as a heavy, silvery metal that is extremely radioactive. It has no stable isotopes, which explains its rareness in nature. Its primary method of decay is alpha decay. It's physical properties are actually very similar to lanthanum and radium, the elements adjacent to it in the periodic table. This could be attributed to the similar number of valence electrons, which determine an atom's physical and bonding properties. It has a boiling point that is neither extremely high or low among the elements of the periodic table at 1050° C. Actinium's atomic weight of 227 indicates that it is neutron rich, bearing almost twice as many neutrons on average as protons. It has an oxidation state of 3+, but few compounds have been successfully created with it.
Actinium is very rare in nature. It has only been discovered naturally in uranium ore (pitchblende). It is naturally the product of U-235 decay. Even in uranium ore it exists in very small quantities. For every pound of uranium ore, there is approximately 1.65x10-7 pounds of actinium. The only isotope that occurs naturally is 227Ac. In comparison with other elements it makes up a microscopic portion of the earth's crust. There is approximately 5.5x10-10 mg for every kg of matter. 
Actinium is also produced synthetically. This is accomplished by bombarding radium atoms with neutrons. The neutrons cause the radium to become unstable and decay into actinium. Because of the quantities that can be produced compared to naturally extracting it from uranium, this is the primary method of obtaining actinium samples. Most actinium produced this way is used for research purposes.
Uses It has been speculated, however, that it could be used in the production of neutrons. Since actinium is neutron rich and unstable, the shedded neutrons could be used in the production of other elements. As actinium is created by bombarding radium with neutrons, so could other particles be created with actinium's neutrons.
Other possible uses include:
- Use in thermal electric generators for spacecraft
- Source of radiation in cancer radiation therapy - There are several isotopes of actinium that could be used for this, but, while many kill cancer cells, they will also accumulate in the bones and liver. While solving the temporary problem of one type of cancer, they may very well cause future cancers because of radioactive emissions.
The Actinide Series
Actinium is the first element in the actinide series of elements on the periodic table. The actinide series stretches from actinium to lawrencium. They are all located in the seventh series and are in the f-block of the periodic table. All members of the actinide series are unstable and are extremely radioactive. They are also very electropositive, meaning that they easily give up electrons in the few bonds that they can form. They primarily combine with nonmetals. Upon being exposed to air, all actinides readily tarnish, losing their lustrous appearance. All the elements show relatively short half lives for radioactive elements.
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