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Americium

Element 95 · Actinide

Specimen

Atomic number
95
Atomic mass
[243]
State at room temperature
Solid
Melting point
1,176 °C
Boiling point
2,011 °C
Density
13.69 g/cm³
Discovered
1944

Mass number of the longest-lived isotope, from IUPAC.1 Other physical data from PubChem.2

Can I eat it?

In food and water
Radioactive. Americium is radioactive. Inside the body it collects in the bones and stays there for a long time. Its radiation can cause bone cancer. 3

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The atom

Am
ShellElectrons
1 (K) 2
2 (L) 8
3 (M) 18
4 (N) 32
5 (O) 25
6 (P) 8
7 (Q) outermost 2
Total95

Configuration [Rn] 5f⁷ 7s²

5f ↑ ↑ ↑ ↑ ↑ ↑ ↑
7s ↑ ↓
A shell diagram: each ring is an electron shell and each dot is one electron. The nucleus holds 95 protons. The outermost shell is shown in red. Electrons do not travel on rings: they fill orbitals, regions where an electron is likely to be found. The boxes are those orbitals for the electrons outside the Rn core, with one arrow per electron.

Related elements

Actinides
Ac Actinium Th Thorium Pa Protactinium U Uranium Np Neptunium Pu Plutonium Cm Curium Bk Berkelium Cf Californium Es Einsteinium Fm Fermium Md Mendelevium No Nobelium Lr Lawrencium

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Sources

  1. 1

    IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW), 2024. Radioactive Elements .

    Mass number and half-life of the longest-lived isotope of the 34 elements with no standard atomic weight.

  2. 2

    National Center for Biotechnology Information (PubChem), 2026. Periodic Table of Elements .

    Electron configuration, melting and boiling points, density and discovery year for all 118 elements.

  3. 3

    Agency for Toxic Substances and Disease Registry (ATSDR), 2004. Americium | ToxFAQs .

    • Inside your body, americium is concentrated in your bones, where it remains for a long time. The radiation given off by americium can change the genetic material of the bone cells and this could result in the formation of bone cancers.