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ChemBench
How much is left, given the half-life?
Radioactive decay follows N = N₀ × (½)^(t/half-life) — after one half-life, half remains; after two, a quarter; after three, an eighth, and so on, regardless of the starting amount.
Carbon-14 dating uses exactly this formula, working backward from the fraction of carbon-14 remaining in an organic sample to determine how many half-lives (and therefore how many years) have passed since the organism died.
Molar mass of any chemical formula (e.g. H2O, C6H12O6, Ca(OH)2).
OpenPercent composition of an element within a chemical formula.
OpenSimplest whole-number ratio formula from elemental masses or percentages.
OpenPercent yield from actual and theoretical reaction yields.
OpenRemaining amount
25
What you entered
Number of half-lives elapsed
11460 ÷ 5730= 2N = N₀ × (½)^(t ÷ half-life)
100 × (½)^2= 25Result
Remaining amount: 25
After 11460 years, 25 out of the original 100 remains.