Americium (Am): electron configuration, atomic mass and facts
Americium (Am) is element 95 of the periodic table, an actinide in period 7 (f-block). Its electron configuration is [Rn] 5f7 7s2, with electrons arranged in shells 2, 8, 18, 32, 25, 8, 2, and its most stable isotope has mass number 243.
▶ Watch Americium’s electrons orbit in the interactive periodic tableAmericium at a glance
| Symbol | Am |
|---|---|
| Atomic number | 95 |
| Atomic mass | [243] u (most stable isotope) |
| Category | Actinide |
| Group | f-block (no group number) |
| Period | 7 |
| Block | f-block |
| Electron configuration | 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f7 6s2 6p6 7s2 |
| Noble-gas shorthand | [Rn] 5f7 7s2 |
| Electrons per shell | 2, 8, 18, 32, 25, 8, 2 |
| Electronegativity (Pauling) | 1.13 |
| State at 20 °C | solid |
Where is Americium on the periodic table?
Americium is in period 7 of the f-block, the actinide row printed below the main table. It has 7 electron shells, and this row is where the 5f subshell fills.
How to work out the electron configuration of Americium
Put 95 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p⁶ (10), 3s² (12), 3p⁶ (18), 4s² (20), 3d¹⁰ (30), 4p⁶ (36), 5s² (38), 4d¹⁰ (48), 5p⁶ (54), 6s² (56), 4f¹⁴ (70), 5d¹⁰ (80), 6p⁶ (86), 7s² (88), 5f⁷ (95). In shorthand, [Rn] stands for the 86 electrons of radon, giving [Rn] 5f⁷ 7s².
How electronegative is Americium?
Americium has a Pauling electronegativity of 1.13, ranking 83 of the 100 elements with a known value (fluorine is highest at 3.98). That is low: it tends to give up electrons and form positive ions.
Frequently asked questions
What is the electron configuration of Americium?
The electron configuration of Americium (Am) is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d10 5f7 6s2 6p6 7s2. In noble-gas shorthand it is written [Rn] 5f7 7s2.
How many electrons does Americium have in each shell?
Americium has 95 electrons arranged in shells as 2, 8, 18, 32, 25, 8, 2.
What is the atomic mass of Americium?
Americium has no stable isotopes. Its most stable isotope has a mass number of 243.
Is Americium a metal?
Yes. Americium is an actinide.
Explore nearby elements
More actinides: Uranium, Neptunium, Plutonium, Curium, Berkelium, Californium. See all elements on the periodic table.