Am
Actinide
Americium
Z 95A 243mass 243
Decay curve
Americium-241
half-life
432.6 years
half-lives elapsed1 half-life
0123456
left
50.0%
real time
433 years
Sample of 240 nuclei
106 leftEach dot is one nucleus. Decay is random for each one — but the pattern that emerges is the exponential curve on the left.
The numbers
| Half-lives | Time elapsed | Remaining | Of 1000 |
|---|---|---|---|
| 0 | — | 100.0% | 1000 |
| 1 | 433 years | 50.0% | 500 |
| 2 | 865 years | 25.0% | 250 |
| 3 | 1,298 years | 12.5% | 125 |
| 4 | 1,730 years | 6.25% | 63 |
| 5 | 2,163 years | 3.13% | 31 |
| 6 | 2,595 years | 1.56% | 16 |
N = N₀ × (½)ⁿ — never exactly zero
Real half-lives, for scale
Thorium-23214.05 billion years
Uranium-2384.47 billion years
Potassium-401.25 billion years
Neptunium-2372.14 million years
Plutonium-23924,110 years
Carbon-145,730 years