If the mass number of an atom is 101, it typically means that it has 101 nucleons (protons and neutrons) in its nucleus. The mass of an atom would depend on the type of atom it is, but in general, the mass of an atom with a mass number of 101 would be greater than 101 atomic mass units (amu), as it also contains electrons orbiting around the nucleus. The specific mass of the atom would depend on its atomic number, which determines the number of protons in the nucleus.