Bi
Post-transition metal
Bismuth
Z 83A 209mass 208.98
Decay curve
Bismuth-214
half-life
19.9 minutes
half-lives elapsed1 half-life
0123456
left
50.0%
real time
19.9 minutes
Sample of 240 nuclei
120 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 | 19.9 minutes | 50.0% | 500 |
| 2 | 39.8 minutes | 25.0% | 250 |
| 3 | 59.7 minutes | 12.5% | 125 |
| 4 | 1.33 hours | 6.25% | 63 |
| 5 | 1.66 hours | 3.13% | 31 |
| 6 | 1.99 hours | 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