The mass of a hydrogen atom is approximately 1.00784 atomic mass units (u) or 1.673 x 10^-24 grams (g). The atomic mass unit is defined as one-twelfth the mass of a carbon-12 atom. Since a hydrogen atom is the lightest atom, it is commonly used as a reference point for atomic mass.
It's important to note that the value provided is an approximation and represents the average mass of a hydrogen atom, considering the different isotopes of hydrogen. The most common isotope, protium (^1H), has a mass of approximately 1.007825 u or 1.673 x 10^-24 g. The other isotopes, deuterium (^2H) and tritium (^3H), have slightly different masses due to the presence of additional neutrons.