Actinium
Definition and meaning of Actinium in chemistry.
![Actinium element card: symbol Ac, atomic number 89, atomic mass [227], electron configuration [Rn] 6d¹ 7s², oxidation states +3, Actinide, group 3, period 7, solid at room temperature.](/assets/images/terms/actinium-chemical-element.webp)
Actinium is a soft, silvery-white radioactive metal with the symbol Ac and atomic number 89. It serves as the very first element of the famous actinide series on the periodic table. The pure metal is highly radioactive and actually glows with a pale blue light in the dark.
In more detail
This eerie blue glow happens because the unstable metal constantly emits highly energetic particles. Actinium sits in period 7 of the periodic table as the heavier analog of lanthanum. It shares remarkably similar chemical properties and behaviors with its lighter lanthanum cousin.
Actinium occurs naturally in incredibly tiny amounts deep inside Earth's rocky uranium ores. It forms naturally only as a temporary radioactive decay product of the uranium-235 isotope. The element lacks any stable isotopes, meaning every version of actinium will eventually decay.
An isotope is a specific version of an element with a unique number of neutrons. Actinium-227 is the most long-lived natural isotope, featuring a relatively brief half-life of 21.77 years. Because natural actinium is extremely scarce, scientists must produce most research samples artificially.
They accomplish this by deliberately hitting radium-226 targets with neutrons inside a nuclear reactor. Actinium's intense radioactivity makes the pure metal exceedingly dangerous for scientists to manipulate safely. The pure metal oxidizes rapidly in normal air to form a tough actinium oxide coating. Its chemistry mostly features the +3 oxidation state, forming colorless compounds that act as strong bases.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Ac |
| Atomic number | 89 |
| Atomic mass | [227] u |
| Category | Actinide |
| State at room temperature | Solid |
| Melting point | 1050 °C |
Medical researchers actively study the actinium-225 isotope for an experimental treatment called targeted alpha therapy. Doctors attach the radioactive actinium to special targeting molecules that seek out aggressive cancer cells. These molecules carry the lethal radiation directly to the tumor to destroy it with precision. This targeted approach kills the cancer while minimizing harmful radiation damage to nearby healthy tissue.
Frequently asked questions
How is actinium obtained for scientific research?
While trace amounts exist in uranium ores, scientists typically synthesize it in nuclear reactors. They produce it through the deliberate neutron bombardment of radium targets.
Why is actinium being used in cancer research?
Certain isotopes of actinium emit highly energetic alpha particles. These particles can destroy targeted cancer cells with incredible precision while sparing the surrounding healthy tissue.
Related terms
Sources & references
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