The three quarks inside a proton account for barely 1% of its mass; the rest is the energy of the gluon field boiling between them. The proton number Z fixes the element — going from 1 to 18 means going from hydrogen to argon — while adding or removing neutrons changes only the mass number A, never the name. The binding energy per nucleon climbs to a peak at iron-56 near 8.8 MeV, and that peak splits the nuclear world in two: below iron, fusion releases energy; above it, only fission does.
The three quarks inside a proton account for barely 1% of its mass; the rest is the energy of the gluon field boiling between them. The proton number Z fixes the element — going from 1 to 18 means going from hydrogen to argon — while adding or removing neutrons changes only the mass number A, never the name. The binding energy per nucleon climbs to a peak at iron-56 near 8.8 MeV, and that peak splits the nuclear world in two: below iron, fusion releases energy; above it, only fission does.
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