# Radioactivity. Radioactivity – Particles are emitted from an unstable nuclei. positron High Energy Photons gamma β-β- Beta αAlpha symbolName β+β+

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Radioactivity – Particles are emitted from an unstable nuclei. positron High Energy Photons gamma β-β- Beta αAlpha symbolName β+β+

Nuclear Equations:

The time taken for the activity, or the number of atoms remaining, to fall by half is called the half-life = half-life

Modified Graph lnN vs time

Equations A = the activity in becquerels (Bq) at time t A 0 = the original activity of the sample ΔN = number of disintegrations Δt = time interval N 0 = the original number of atoms in the sample. N = the number of atoms remaining after time t λ = the decay constant e = mathematical constant

Deriving the half-life equation

Example: A sample of radioactive isotope originally contains 1.0 x 10 24 atoms and it has a half-life of 6.0 hours. Find: a)The decay constant b)The initial activity c)The number of atoms remaining after 12 hours d)The number of atoms remaining after 30 minutes