So I am taking the second semester of intro physics and Moles,Molecular mass, Number of Molecules is killing me. I am not really able to solve my homework because I can never get these quantities down. I asked my professor for help during offie hours, however he said he teaches physics not chemistry. I have never had a chemistry. This is what I understand so far. N=nNa where N=number of molecules, n=number of moles in substance, and Na is Alvogadros constant. I know that if I look at a periodic table, I can find the mass (is this molecular mass/atomic mass)? Say I want the molecular mass of Helium. From the Periodic Table i see the atomic mass 1.00794u. I take this atomic mass and multyply by 1.66x10^-23 and I get the molecular mass in kilograms. How do I find the moles?