Definition:Radioactive Decay/Half-Life

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Definition

The half-life of a radioactive isotope is the time it takes for exactly half of an arbitrary quantity of that isotope to undergo radioactive decay.

Thus it is the time it takes for exactly half of an arbitrary quantity of that isotope to remain.


Examples

This page lists isotopes of some radioactive elements and their half-lives.

Rubidium-$87$    $48.8 \times 10^9$ years             
Uranium-$238$    $4.5 \times 10^9$ years             
Potassium-$40$    $1.251 \times 10^9$ years             
Carbon-$14$    $5\,730 \pm 40$ years             


Sources