Enter your isotope's half-life (with your choice of time unit) and molar mass to calculate its specific activity — the radioactivity per gram of material. You'll also get the decay constant, atoms per gram, and a handy mass-based conversion in your preferred output unit (Bq or Ci, at whatever scale fits your numbers).
Specific Activity
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Half-life (seconds)
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Decay Constant
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Atoms per Gram
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Specific activity is the radioactivity per unit mass of a radioactive material, typically expressed in Bq/g or Ci/g. It indicates how much radioactive decay occurs per gram of the substance.
Specific activity is calculated using the formula: A = (λ × N₀)/M, where λ is the decay constant (ln(2)/t₁/₂), N₀ is Avogadro's number, and M is the molar mass. The decay constant relates directly to the half-life.
Becquerel (Bq) is the SI unit for radioactivity, representing one decay per second. Curie (Ci) is the older unit, where 1 Ci = 3.7 × 10¹⁰ Bq. Bq-based units are preferred in scientific applications.
Molar mass is essential for converting from atomic-level decay rates to mass-based specific activity. It represents the mass of one mole of the radioactive isotope in grams.
The calculator converts all half-life inputs to seconds internally before calculating the decay constant. Longer half-lives result in lower specific activity values since the material decays more slowly.
The decay constant (λ) represents the probability of decay per unit time. It's calculated as ln(2)/half-life and is fundamental to determining specific activity and radioactive decay rates.
Yes, the calculator provides output in both SI (Bq-based) and non-SI (Ci-based) units with various scale multipliers like kBq, MBq, GBq, µCi, mCi to match your preferred units.
This shows the number of radioactive atoms present in one gram of the material. It's calculated using Avogadro's number and helps understand the atomic composition of the radioactive sample.