25.4 Radioactive decay calculations

• The number of undecayed nuclei in the sample at a time= The original amount of undecayed nuclei x e^ - decay constant x time.
• The number of nuclei can be determined using a mass spectrometer or calculated from it's mass.
• The activity of a sample at a time= original activity x e^ - decay constant x time
• The half life of a substance can be calculated by plotting a graph of corrected count rate against time.