For protons, the sum of the rest masses of the three valence quarks (two up quarks and one down quark) is approximately 9.4 MeV/ c, while the proton's total mass is about 938.3 MeV/ c. In the standard model, this "quark current mass" can nominally be attributed to the Higgs interaction, For neutrons, the sum of the rest masses of the three valence quarks (two down quarks and one up quark) is approximately 11.9 MeV/ c, while the neutron's total mass is about 939.6 MeV/ c. Considering that nearly all of the atom 's mass is concentrated in the nucleons, this means that about 99% of the mass of everyday matter (baryonic matter) is, in fact, chromodynamic binding energy.