AMU v Proton Mass

[sofiarips]

Why is the atomic mass unit (1.66 x 10^-27 kg) smaller than both the mass of a proton (1.673 x10^-27 kg) and a neutron (1.675 x10^-27 kg)? Why is in't amu closer to an average of proton and neutron masses?

[laurence14b2f]

Hey! The amu is a kind of lighter than a proton or a neutron since it accounts for the mass of particles within the nucleus, but not their entire mass. It takes into account the average mass of protons and neutrons along with electrons, which are much lighter. This average helps in expressing atomic masses in a more understandable way. So, it's not exactly the same as the sum of proton and neutron masses, but a pretty close approximation for atomic calculations.

[205969338]

The atomic mass unit (amu) is defined based on the carbon-12 isotope. One atomic mass unit is one-twelfth the mass of a carbon-12 atom. This is because carbon-12 is abundant, and its mass is close to the average mass of a proton or neutron.