Ahalf-life of a radioactive substance is the amount of time needed for one half of to decay into a stable isotope.
a) the neutrons in the nuclei
b) its beta particles
c) the nuclei in a sample

A half-life of a radioactive substance is the amount of time needed for one hald of the nuclie in a sample to decay into a stable isotope.Many protons and neutrons disturb the balance of binding energy from a strong nuclear forces resulting for the nucleus to be unstable. To be in a balance state, the unstable nucleus will give off a proton or neutron through radioactive decay.