Americium Properties (23 Facts You Should Know)

Americium is a synthetic transuranic and radioactive element. It undergoes radioactive disintegration due to having an unstable nucleus. Let us discuss its properties elaborately.

Americium is a soft and silvery-white element with a double hexagonal close-packed crystal structure. Most of this element is produced from uranium or plutonium after bombardment with neutrons in nuclear reactors. Americium forms two of its stable oxides, AmO and Am2O3.

Let us focus on the period, group, isotopes, ionization energies, electronegativity, radius, and magnetic behavior of americium in detail.

Americium Symbol

The chemical symbol of americium is Am. This short notation comes from the first two alphabets of the word “americium”.

Americium Group in Periodic Table

Americium belongs to the group of actinide elements and the actinide group elements are written under the periodic table separately like the lanthanide elements.

Americium Period in Periodic Table

Americium belongs to the 7th period in the periodic table between plutonium and curium.

Americium Block in Periodic Table

Americium is an f-block element because it has a half-filled f-orbital (5f7) and the last electron of americium enters into the f-orbital.

Americium Atomic Number

Americium has an atomic number of 95 because it has 95 protons and a much higher number of neutrons (146) in its nucleus. Due to this large difference between the number of protons and neutrons, it has an unstable nucleus.

Americium Atomic Weight

Americium has an atomic mass of 243.061380 amu (atomic mass unit) which is considered the mass of one americium atom. But due to the radioactive nature of americium, this heavier nucleus is decayed into relatively lower masses.

Americium Electronegativity according to Pauling

Americium shows an electronegativity value of 1.3 on the Pauling scale. But it shows a different electronegativity value of 1.2 in Allred Rochow’s electronegativity scale. Both values are similar to the other elements of the actinoid group.

Americium Atomic Density

Americium has an atomic density of 12 g/cm3 at room temperature.

Americium Melting Point

Americium has a very high melting point of 1449 K or 11760C.

Americium Boiling Point

The boiling point of americium is also very high 2880K or 26070 C like its melting point.

Americium Van der Waals Radius

Americium has a Van der Waals radius of 244 pm and it has an atomic radius of 173 pm.

Americium Ionic/Covalent Radius

Americium has a covalent radius (half of the distance between two atoms attached through covalent bonds) of 180 pm and it has different ionic radii for different ions which are listed below-

IonCoordinationIonic radius (pm)
Am (II)6111.5
Am (IV)699
Am (II)8140
Am (III)8123
Am (IV)8109
Ionic Radii of Americium

Americium Isotopes

Isotopes have the same atomic numbers, but they differ in the number of neutrons. They belong to the same group and period in the periodic table. Let us find out the isotopes of Am.

IsotopesAbundance (in %)Decay mode
241AmsynSpontaneous fission (SF), α, isomeric transition (IT)
242m1AmsynSF, α
243AmsynSF, α
Isotopes of Americium

Americium Electronic Shell

Electronic shells are defined as the different energy states to place the electrons outside the nucleus. Let us find out the electronic shells of americium.

Americium has a total of 95 electrons in its seven electronic shells. They are arranged in those seven shells in 2,8,18,32,25,8, and 2 fashions.

Americium Energy of First Ionization

Americium has the first ionization energy of 576.39 KJ/mol.

Americium Energy of Second Ionization

Americium has the 2nd ionization energy of 1158 KJ/mol which means it needs 1158 KJ/mol energy to remove the 2nd electron from its valence shell.

Americium Energy of Third Ionization

Americium has the 3rd ionization energy of 2161 KJ/mol which indicates it needs 2161 KJ/mol energy to lose its loosely bound valence electrons.

Americium Oxidation States

Americium can exist in variable oxidation states which are written below-

  • +3 (most common and most stable oxidation state)
  • +4
  • +5
  • +6

Americium Electron Configurations

Americium has a electron configuration which is [Rn] 5f7 7s2.

Americium CAS Number

Americium has the CAS registry number (authentic numeric identifier which can contain up to 10 digits) 7440-35-9.

Americium ChemSpider ID

Plutonium has the ChemSpider ID (ChemSpider is a free chemical structure database) 22405.

Americium Chemical Classification

Americium can be chemically classified as an f-block element which is also known as an actinoid series element or actinide element which possesses a radionuclide.

Americium State at Room Temperature

Americium is a solid compound at room temperature (200 C) in its pure form.

Is Americium paramagnetic?

An element can be paramagnetic if it has unpaired electrons in it because these unpaired electrons are attracted by the external magnetic field. Let us explain it in detail.

Americium is a paramagnetic compound because it has 7 unpaired electrons (5f7) in its electron configuration which are attracted by the external magnetic field and show paramagnetism.

americium properties
Unpaired Electrons Americium


One of the isotopes of americium (Am-241) is used in the household smoke detector. It is also used in spacecraft as a source of power for its heat generation capability (114.7 mW/g). Americium is also applied in nuclear batteries for its high nuclear fission rate.

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