A closed vessel with rigid walls contains 1 mol of $_{92}\ce{U}^{238}$ and 1 mol of air at 298K. Considering complete decay of uranium to $_{82}\ce{Pb}^{206}$, the ratio of final pressure to initial pressure of system at 298K is?
The solution of this question is that during this decay, 8 moles of alpha particles will be emitted, so total moles of gas will be 9. At constant temperature and volume, pressure is proportional to moles of gas. So the answer is 9.
My question is: are helium nuclei considered gas molecules, and should we count them while finding $n$ in the ideal gas equation? My thought process for this question was to find out the number of $\beta^{-}$ particles (electrons) emitted (which is 6 here) and then figure out that they would combine with 3 helium nuclei to form 3 helium atoms. Then I would use the ideal gas equation and the answer would come out to be 7.