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RADIOACTIVITY 2
Activity of isotopes
Activity is the number of decays per second.
It is measured in Becquerels (Bq). 1 Curie (Ci) = 3.7 x 1010 Bq. Everything emits some kind of radiation
and therefore has some kind of activity.
U-238 activity
1kg U-238 emits 1.26 x 107 α particles each second so it’s activity is:
1.26 x 107 Bq = 12.6 MBq 0.0034 Ci = 3.4 mCi
Every second 1.26 x 107 U-238 atoms are converted into 1.26 x 107 Th-234 atoms and 1.26 x 107 alpha particles are emitted.
Half-life As the atoms decay, the original
element changes into a new element.
The time taken for exactly half the original atoms to decay is called the half-life of the isotope.
The higher the activity the shorter the half-life.
The lower the activity the longer the half-life.
4 atoms and 400 atoms with half-lives