What is the approximate atomic mass unit (amu) of hydrogen (1H)?

The atomic mass of hydrogen, specifically the most common isotope known as protium (1H), is approximately 1.0080 amu. This value reflects not just the mass of the single proton that makes up the nucleus of hydrogen but also accounts for the presence of the electron surrounding it. In addition, most atomic weights are averaged values that take into account the natural abundance of different isotopes.

Hydrogen has isotopes like deuterium (2H), which has one neutron and is heavier, and tritium (3H), which has two neutrons and is even heavier. Since the atomic mass unit is an average of the isotopes present in nature, the weight goes slightly above 1 amu because of the contribution from these isotopes and the binding energy that affects the mass slightly. Therefore, the value of 1.0080 amu accurately represents the average atomic mass of hydrogen in the natural environment, making this answer the best choice given the context of atomic mass.