The decay of a sample of a radioactive isotope is said to be random and spontaneous. Explain what is meant by the decay being:
random
spontaneous.
A radioactive isotope X has a half-life of 1.4 hours. Initially, a pure sample of this isotope X has an activity of 
. Determine the activity of the isotope X in the sample after a time of 2.0 hours.
.
