Answer:
Explanation: So, the atomic number is the number of protons present in an atom. For example, Helium's atomic number is 2, meaning it only has 2 protons. In most cases, the number of nuetrons and protons are equal, so Helium (usually) has 2 protons and 2 nuetrons - this is the nucleus. The atomic mass, or mass per nucleon is the proton and nuetron added together, so the atomic mass of Helium is about 4. Therefore, on the periodic table, as the atomic number increases by 1, the atomic mass increases by about 2 (the atomic mass is an average so it's not exact).