Americium (Am): Electron Configuration, Properties and Uses
Americium (Am): Electron Configuration, Properties and Uses
Electron configuration [Rn] 7s2 5f7 · f-block, actinide series · period 7 · Ar [243]
Americium data
- Atomic number
- 95
- Relative atomic mass
- [243]
- Group
- – (actinide series)
- Period
- 7
- Block
- f
- Category
- Actinide
- Electron configuration
- [Rn] 7s2 5f7
- Full configuration
- 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7
- Electrons per shell
- 2, 8, 18, 32, 25, 8, 2 (K L M N O P Q)
- Valence electrons
- 2 (in the outer shell)
- Electronegativity (Pauling)
- 1.3
- First ionisation energy
- 5.993 eV
- Atomic radius (van der Waals)
- 244 pm
- State at room temperature
- Solid
- Melting point
- 1176 °C
- Boiling point
- 2011 °C
- Density
- 13.69 g/cm³
- Common oxidation states
- +6, +5, +4, +3
- Discovered
- 1944
Source: PubChem (NIH, accessed 13 Nov 2026); atomic mass: IUPAC standard atomic weight.
Electron shell diagram
K 2 · L 8 · M 18 · N 32 · O 25 · P 8 · Q 2
Orbital diagram (outer electrons)
About americium
Americium, symbol Am, is element number 95 in the periodic table. It belongs to the actinide series in period 7 (f-block), usually shown below the main table. The element was discovered in 1944. It is named after the Americas. Americium is a solid at room temperature, melting at 1176 °C and boiling at 2011 °C.
Americium electron configuration
The electron configuration of americium is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7, or in short [Rn] 7s2 5f7. Its electrons occupy 7 shells: K = 2, L = 8, M = 18, N = 32, O = 25, P = 8, Q = 2. As an actinide, americium fills the 5f subshell. Its outer 7s subshell holds 2 electrons; valence electrons for this series are not assigned by the usual group rule. When it forms cations, electrons leave the outermost subshell first: Am3+ = [Rn] 5f6.
Filling order: 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)
Uses of americium
Well-known applications of americium include Am-241 in ionisation smoke detectors and industrial thickness gauges.
Safety
Americium is radioactive. Using, storing or transporting radioactive material requires a licence from the national regulator (BAPETEN in Indonesia). Always read the safety data sheet (SDS) before working with a chemical.
Other actinides
Frequently asked questions
What is the electron configuration of americium?
The electron configuration of americium (Am, atomic number 95) is 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f7, or [Rn] 7s2 5f7 in short. By shell: 2, 8, 18, 32, 25, 8, 2.
How many valence electrons does americium have?
Americium has 2 electrons in its outer shell. For lanthanides and actinides, valence electrons are not assigned by the usual group rule.
Which group and period is americium in?
Americium is in the actinide series, period 7, f-block.
What is the atomic mass of americium?
Americium has no stable isotope, so the mass number of its longest-lived isotope, [243], is given.
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