Transition metal

Ruthenium

Z 44A 101mass 101.07

Decay curve

Ruthenium (illustrative)

half-life

not measured here

half-lives elapsed1 half-life

0123456

left

50.0%

in half-lives

1 t½

Ruthenium has no radioactive isotope in this lab's data, so the curve shows the mathematics every nucleus follows. Pick uranium, radon or cobalt to read real numbers off the same curve.

Sample of 240 nuclei

116 left

Each 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	Remaining	Of 1000
0	100.0%	1000
1	50.0%	500
2	25.0%	250
3	12.5%	125
4	6.25%	63
5	3.13%	31
6	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