Americium
Definition and meaning of Americium in chemistry.
![Americium element card: symbol Am, atomic number 95, atomic mass [243], electron configuration [Rn] 5f⁷ 7s², oxidation states +3, Actinide, f-block, period 7, solid at room temperature.](/assets/images/terms/americium-chemical-element.webp)
Americium is a synthetic, highly radioactive element with the symbol Am and atomic number 95. It is a dense, silvery metallic member of the actinide series. This purely human-made metal is located directly after plutonium on the periodic table. This metal has a melting point of 1176 degrees Celsius and is highly toxic.
In more detail
Americium is a soft metal that slowly loses its shine in dry air. This element does not occur naturally in the earth's crust. Instead, nuclear reactors make it by hitting plutonium targets with neutrons.
The metal usually takes a +3 oxidation state during chemical reactions. However, it can also form compounds with oxidation states from +2 to +7. Americium belongs to the f-block of elements.
Its chemical properties are very similar to the lanthanide element europium, which sits above it. Many students believe synthetic elements have no real uses, but americium is a major exception. In fact, americium is the only synthetic element that people can find inside their homes.
It emits alpha particles, which are heavy, positively charged helium nuclei. These particles travel a short distance before stopping. Because of this high-energy alpha decay, a small sample of the metal glows in the dark.
It also releases heat as it decays. Scientists must use thick lead shielding and protective boxes to handle this element safely.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Am |
| Atomic number | 95 |
| Atomic mass | [243] u |
| Category | Actinide |
| State at room temperature | Solid |
Household ionization smoke detectors contain a tiny amount of the americium-241 isotope. The americium releases alpha particles that ionize the air molecules inside a small sensor chamber. This ionization creates a steady electrical current between two metal plates. When smoke enters the detector, the smoke particles attach to the ionized air molecules. This blocks the current, which triggers the loud alarm to warn the family of a fire.
Frequently asked questions
Is the radioactive americium in smoke detectors safe for my family?
Yes, it is safe because the alpha radiation cannot travel more than a few inches in air. The plastic case of the detector easily blocks the radiation from escaping.
How do scientists create americium?
Scientists place plutonium inside a nuclear reactor and hit it with a high number of neutrons. The plutonium atoms absorb these neutrons and undergo beta decay to become americium.
What is the most stable isotope of americium?
The most stable isotope is americium-243, which has a half-life of 7370 years. It decays slowly by releasing alpha particles to form neptunium-239.
Related terms
Sources & references
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