Americium (Am)

Americium is a transuranic element with the symbol Am and atomic number 95 in the periodic table of elements that belongs to the family of actinides. This radioactive substance was discovered as the fourth synthetic transuranium element in the list of fifteen radioactive metallic elements that include actinium, thorium, protactinium, uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium.

Chemical and Physical Properties of Americium 

Atomic number95
Atomic weight (mass)(243) g.mol-1
Group (number)None
ColorSilvery-white soft synthetic metal
Physical stateSolid at room temperature
Half-life432.2 years
Electronegativity according to Pauling1.3
Density13.67 at 20°C
Melting point994 °C
Boiling point2607 °C
Van der Waals radiusUnknown
Ionic radiusUnknown
Most characteristic isotopeAmericium-241, Americium-243
Electronic shell[Rn] 5f7 7s2
The energy of the first ionization578 kJ.mol-1
The energy of the second ionizationn/a
Discovery dateIn 1945, by Glenn Seaborg

Americium is a synthetic (i.e. man-made) extremely radioactive soft silver metal that is resistant to alkalis. With an atomic mass of (243) g.mol -1, electron configuration [Rn] 5f77s2, and an unknown atomic radius, this substance reacts with acids, air, and water vapor. Americium is a toxic and radiotoxic element that exhibits magnetism when exposed to both low and high temperatures. It easily reacts with oxygen (O2) and radiates both alpha and gamma rays. In addition, it shares some thermodynamic properties with neptunium, plutonium, and uranium.

How Was Americium Discovered?

Americium was discovered in 1944 by the University of Chicago chemists – Glenn T. Seaborg, Ralph James, Stanley G. Thompson, Leon O. Morgan, and Albert Ghiorso (USA). The Argonne National Laboratory, i.e. the metallurgical laboratory at this American university was the place where americium was first distinguished as a chemical element. 

It was first introduced in 1945, during the Manhattan Project, a secret project of the U.S. government during World War II, aimed at making an atomic bomb. 

How Did Americium Get Its Name?

Americium was discovered in the United States and it’s named after North America. Another reason for being named after North America is the fact that americium comes under lanthanide europium (Eu 63) in the periodic table of elements, which got its name after Europe. 

Also, the name follows the pattern of naming newly discovered chemical elements after the countries of discovery or the scientists who have brought a new chemical element to the knowledge of the World. Other such names are the aforementioned europium, and curium (Cm), named after Marie and Pierre Curie. 

Where Can You Find Americium?

Americium can be found in trace amounts in uranium minerals. It’s also produced by bombarding plutonium-239 with neutrons in nuclear reactors. Having a half-life of 432.2 years, this chemical element has few practical applications, among which we find the production of nuclear fuel. It is also radioactive, and while small amounts of americium dioxide (AmO2) used in smoke detectors create alpha radiation to detect fire, americium will not irradiate humans.

Smoke Detectors

Smoke detectors can often be the thin line between life and death when it comes to fire. Early signals of smoke reduce the chance of the most tragic scenario happening. Alarms detect and warn people of imminent danger at an early stage, giving them the necessary time to react or to run away from danger.

The smoke detector is one of those exceptional inventions that have a rather low price due to massive production. All smoke detectors consist of two basic parts:

  • a sensor that detects smoke;
  • a very loud electric bell that alerts or wakes people up.

What Are the Types of Smoke Detectors?

 The two most common types of smoke detectors, which are separated by a mechanism, are:

  •  photoelectric smoke detector;
  •  ionic smoke detector.
Photoelectric Smoke Detector

A photoelectric smoke detector uses a sensor similar to the one used in a device called a ‘photobeam detector’, often used in some American stores. On one side of the store, there is a white light and a lens or a low-power laser installation, while on the other side of the store there is a photodetector that can detect this light. When the light is blocked by smoke, the photodetector detects this lack of light and triggers the alarm. 

Ionic Smoke Detector

Ionizing smoke detectors are better at detecting sudden fires. Namely, inside this type of smoke detector, there are two perpendicularly positioned plates. A small amount of radioactive americium is found between the plates so they can create a flow of electrically charged ions between them. When there is smoke in a facility with an ionic smoke detector, it triggers the alarm by obstructing the flow of ions. 


Smoke detector devices are often connected to an alarm system that has been pre-installed. It can certainly be useful in practice. If the smoke detector fails for any reason, an activation signal would sound via the alarm system reporting a system error. This can certainly be valuable information because it significantly reduces the fire risk.

Medical and Industrial Uses of Americium

Despite being highly toxic and radioactive, the isotope Americium-241 (241Am, Am-241) is implemented in radiography, as a source of radioactive alpha particles and portable gamma-rays used in the diagnostics of malign conditions.

How Dangerous Is Americium?

Exposure to high concentrations of americium can result in severe health conditions, such as damage to the lungs, bones, kidneys, and dysfunction of the thyroid gland because these organs absorb the radioactive americium particles most easily. However, the alpha-particles cannot get into the body through the skin, since they have a short span of movement when released. Generally, these are low levels of exposure to americium and are not considered to be a serious health hazard. Americium is far more dangerous if inhaled.  

The danger of inhaling americium contaminated air or dust particles of this radioactive element via contaminated water, food, or soil is increased during an event of a nuclear accident. However, people who work in nuclear facilities or live nearby are also exposed to some levels of the americium-241 isotope.  

When inhaled, americium can stay in the lungs from a few hours to a few months, depending on the form of the radioisotope. On the other hand, if americium enters the body via contaminated food or water, a small amount of it may transition from the gastrointestinal tract into the bloodstream. Upon prolonged exposure to americium, it can accumulate in the bones, liver, and other organs, where it may remain for decades or even years and undergo radioactive decay. In this way. The radioactive alpha-particles of americium change the genetic material of the cells, which may result in cancer of the affected tissue. 

Environmental Effects of Americium

Due to the long decay of its isotopes, americium stays in the environment for a very long time. Hence, it imposes a serious environmental hazard. Being a radioactive element, this silvery-shiny metal is extremely harmful to nature, as it may remain in the soil, water, or air for 30 to 40 years. 

Radioactive americium pollution occurs as a result of the testing of nuclear weapons or atomic bomb explosions, the use of americium in nuclear reactors, but also from landfills that have used smoke detectors. Americium released from nuclear weapons tests may remain in the atmospheric air for several decades. 

Isotopes of Americium

This chemical element counts 8 nuclear isomers and 19 isotopes. None of the americium isotopes occurs naturally and neither one of them is in a stable form. 

Americium-243 is the most stable radioisotope of americium that decays into plutonium-241. The half-life of americium-243 is about 7,370 years. It decays into neptunium-239 and is three times more active than radium.

Since these isotopes continuously give off radiation, it changes them into isotopes of the same or different elements. 

  • 229Am             229.045249909 ± 0.000093772
  • 229Amp 229.045249909 ± 0.000093772
  • 230Am             230.046089 ± 0.000143 [Estimated]
  • 231Am             231.045529 ± 0.000322 [Estimated]
  • 232Am             232.046527 ± 0.000322 [Estimated]
  • 233Am             233.046445 ± 0.000109 [Estimated]
  • 234Am             234.047731 ± 0.00017 [Estimated]
  • 235Am             235.047907371 ± 0.00005603
  • 236Am             236.049427 ± 0.00012 [Estimated]
  • 236Amm 236.049427 ± 0.00012 [Estimated]
  • 237Am             237.049995 ± 0.000064 [Estimated]
  • 238Am             238.051982607 ± 0.000054428
  • 238Amm 238.051982607 ± 0.000054428
  • 239Am             239.053022803 ± 0.000002128
  • 239Amm 239.053022803 ± 0.000002128
  • 240Am             240.055298444 ± 0.000014849
  • 240Amm 240.055298444 ± 0.000014849
  • 241Am             241.056827413 ± 0.000001195
  • 241Amm 241.056827413 ± 0.000001195
  • 242Am             242.059547428 ± 0.0000012
  • 242Amm 242.059547428 ± 0.0000012
  • 242Amn 242.059547428 ± 0.0000012
  • 243Am             243.061379940 ± 0.00000149
  • 243Amm 243.061379940 ± 0.00000149
  • 244Am             244.064282964 ± 0.000001601
  • 244Amm 244.064282964 ± 0.000001601
  • 244Amn 244.064282964 ± 0.000001601
  • 244Amp 244.064282964 ± 0.000001601
  • 245Am             245.066452890 ± 0.000002025
  • 245Amm 245.066452890 ± 0.000002025
  • 246Am             246.069774 ± 0.000019 [Estimated]
  • 246Amm 246.069774 ± 0.000019 [Estimated]
  • 246Amn 246.069774 ± 0.000019 [Estimated]
  • 247Am  247.072092 ± 0.000107 [Estimated]
  • 248Am             248.075752 ± 0.000215 [Estimated]
  • 249Am             249.078480 ± 0.00032 [Estimated]

Chemical Compounds of Americium

Americium can be found in compound form with halides, iodides, oxides, and hydrides:

  • Americium trifluoride: AmF3
  • Americium tetrafluoride: AmF4
  • Americium dichloride: AmCl2
  • Americium trichloride: AmCl3
  • Americium tribromide: AmBr3
  • Americium diiodide: AmI2
  • Americium triiodide: AmI3
  • Americium oxide: AmO
  • Americium dioxide: AmO2
  • Diamericium trioxide: Am2O3
  • Hexa-aquo-di-chloro-americium chloride: AmCl3.6H2O

5 Interesting Facts And Explanations About Americium

  1. Americium has the widest range of oxidation states among the other elements belonging to the family of actinides in the periodic table. 
  2. The scientific investigations of transuranium of research scientist of the University of California, Berkeley, Glenn Theodore Seaborg led him to the Nobel Prize in Chemistry in 1951. Due to his efforts in the field of chemistry, the periodic table of elements got the current arrangement of the actinides. 
  3. The discovery of americium was first announced via live radio broadcast of the show “Quiz Kids”. 
  4. Atomic bombs, nuclear reactors, and industrial equipment are some of the artificial sources of radiation.
  5. The radioactive energy of the alpha-particles that are emitted by americium is 5.4 MeV.