Yes, that's correct! Most of an atom's mass is found in its protons and neutrons, which together are referred to as nucleons. Protons and neutrons reside in the nucleus of the atom, while electrons, which are much less massive than protons and neutrons, orbit around the nucleus.
To put it into perspective, while an electron has a mass of about \(9.11 \times 10^{-31}\) kilograms, a proton has a mass of about \(1.67 \times 10^{-27}\) kilograms, and a neutron is slightly more massive, at about \(1.68 \times 10^{-27}\) kilograms. Since protons and neutrons account for the bulk of an atom's mass, the mass of an atom is primarily determined by the number of protons and neutrons it contains.