Background Info: A radioactive isotope is an element that has a nucleus that is so unstable, that
it causes the substance to decay into a different
element. The half-life of a radioactive isotope is how
long it will take for that substance's mass to
decrease by half. Explained differently, after 1 half-
life period of time, 50% of the substance is gone.
The exponential decay equation used to determine
how much of a substance that is left, y, is:
y = a(0.5)*
=
a is the starting mass
x is the number of half-lives that have passed.
(EX. If the half life is 3 days, then 6 days would be 2
half lives and 9 days would be 3 half-lives)
Question 7 (1 point)
lodine-131 is a very useful radioactive isotope
that is used to locate and treat cancerous tumors
in the body and has a half life of 8 days. If a
radiologist were to use 64 mg of this isotope, how
much of it would still be left after 32 days?