A nucleon is one of the particles that make up the nucleus of the atom. Protons and neutrons are nucleons, and the neutronis the electrically neutral nucleon.

A nucleon has more mass when it is not bound to the nucleus of an atom.

When the nucleon is bound to other nucleons the binding energy that keeps them together comes from the mass of the nucleon. Therefore the mass of a single nucleon will be smaller in an atom than on it's own.

A nucleon is a name for a group of two important subatomic particles. They consist of both neutrons and protons.

A. N. Antonov has written:

'Nucleon correlations in nuclei' -- subject(s): Nuclear structure, Nucleon-nucleon interactions

'Nucleon momentum and density distributions in nuclei' -- subject(s): Angular distribution (Nuclear physics), Angular momentum (Nuclear physics), Nuclear structure

The mass of the nucleon is decreased; the difference is released as energy.