State what is meant by radioactive decay.
The variation with time 
of the number 
of technetium-101 nuclei in a sample of radioactive material is shown in the figure below.
Use the figure above to determine the activity, in 
, of the sample of technetium-101 at time 
. Show your working.
Without calculating the half-life of technetium-101, use your answer in (i) to determine the decay constant 
of technetium-101.
-particles, 
-particles, or 
-ray photons by an unstable nucleus.
.
.
