Periodic TableAmericium (Am)
Americium is an actinide with atomic number 95, in period 7, in the f-block of the periodic table. Its atomic mass is 243 u and its electron configuration is [Rn] 5f⁷ 7s². Solid at 25 °C.
Key facts
| Atomic number | 95 |
|---|---|
| Atomic mass | 243 u |
| Category | Actinide |
| Period | 7 |
| Group | f-block, no group number |
| Block | f |
| Electron configuration | [Rn] 5f⁷ 7s² |
| Electrons per shell | 2, 8, 18, 32, 25, 8, 2 |
| Electronegativity (Pauling) | 1.3 |
| Oxidation states | +2, +3, +4, +5, +6, +7common in bold |
| State at 25 °C | Solid |
| Melting point | 1449 K1175.85 °C |
| Boiling point | 2284 K2010.85 °C |
| Density | 13.69 g/cm³ |
Atomic properties
| First ionization energy | 5.974 eV |
|---|---|
| Electron affinity | --- |
| Atomic radius | 173 pm |
| Covalent radius | 180 pm |
| Van der Waals radius | 244 pm |
| Common ions | Am³⁺, Am⁴⁺ |
| Protons, neutrons, electrons | 95, 148, 95 |
Physical and thermal properties
| Molar volume | 17.63 cm³/mol |
|---|---|
| Heat of fusion | 14.39 kJ/mol |
| Heat of vaporization | --- |
| Specific heat | --- |
| Thermal conductivity | 10 W/(m·K) |
| Thermal expansion | --- |
| Mohs hardness | --- |
| Young’s modulus | --- |
| Crystal structure | Simple hexagonal |
| Magnetic type | Paramagnetic |
Identification and history
| CAS number | 7440-35-9 |
|---|---|
| Latin name | Americium |
| Discovered by | G. Seaborg, R. James, L. Morgan, A. Ghiorso · 1944 |
| Named by | --- |
Natural isotopes
Americium has no stable isotopes: every isotope is radioactive.
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
See Americium in the app
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