Hello!
The half-life is the time of half-disintegration, it is the time in which half of the atoms of an isotope disintegrate.
We have the following data:
mo (initial mass) = 43 g
m (final mass after time T) = ? (in g)
x (number of periods elapsed) = ?
P (Half-life) = 20 minutes
T (Elapsed time for sample reduction) = 80 minutes
Let's find the number of periods elapsed (x), let us see:






Now, let's find the final mass (m) of this isotope after the elapsed time, let's see:




I Hope this helps, greetings ... DexteR! =)
<span>The mass number given on
the periodic table is a weighted average of all the isotopes. You get the exact mass of
an isotope by adding the protons(atomic number) to the
number of neutrons in that isotope.</span>
Because if an electron was in an atom, it would allow two atoms to combine without exploding and disentigrating, therfore there would be no suck thing as nuclear fission (nuclear bomb)