Radioactive decay is both spontaneous and random. State what is meant by:
spontaneous decay
random decay
Strontium-90 (
) is an unstable nuclide. The activity of a sample of 
of strontium-90 is 
.
Determine the decay constant 
of strontium-90.
The activity of the sample after a time of 1.0 half lives is found to be greater than the expected 
. Suggest a possible reason for this.
.
