* Helium's Atomic Mass: Helium (He) has an atomic mass of approximately 4 atomic mass units (amu).

* Four Times the Mass: Four times the atomic mass of helium would be 4 amu * 4 = 16 amu.

* The Element: The element with an atomic mass closest to 16 amu is oxygen (O), which has an atomic mass of approximately 16 amu.

Therefore, oxygen has an atomic mass that is roughly four times that of helium.