Answer:
Hydrogen.
Step-by-step explanation:
Hydrogen has greater mass and it's bigger than helium because as we move from left to right on the periodic table, atomic size decreases. Hydrogen atom is normally signified than H2 which is bigger than an atom of helium.
Also hydrogen has an atomic radius of 53pm while Helium has an atomic radius of 31 pm. Therefore the mass of helium is smaller than that of hydrogen.