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