They don’t, what you even on about
When an atomic nucleus emits an alpha particle it decay into an atom with atomic number 2 less and mass number 4 less. Thus Thorium 230 decay as follows.
230 90Th -------> 226 88Th + 4 2 He
thorium is in the atomic number 90 thus it during alpha decay it reduces to atomic number 88 while its 230 mass number reduces to 226
The answer to the problem is 11.615
So the ideal gas law is pv=nrt
The letter n stands for the number of moles. divide both side by rt to isolate.
pv/rt=n