What is the mass defect of oxygen-16? Assume the following: The atomic number of oxygen-16 is 8. The atomic mass of oxygen-16 is 15.9994 atomic mass units. The mass of one proton is 1.0073 atomic mass units. The mass of one neutron is 1.0087 atomic mass units.

To solve for the mass defect of the given atom, add up the individual masses of the nucleons, protons and neutrons. In this case, the total mass of the nucleons is solved through 8x (1.0073 + 1.0087) and is equal to 16.128. Subtracting the mass of the intact nucleus which is 15.9994 gives 0.1286. Thus, the mass defect is 0.1286.