Question: what are the total number of protons and neutrons in a water molecule?
Answer: Each hydrogen atom has 1 proton, no neutrons (assume all H are protonium) and 1 electron. The oxygen atom has 8 protons, 8 neutrons (most abundant isotope) and 8 electrons. Therefore, the water molecule has: 8 + 1 + 1 = 10 protons.