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The helium-four atomic nucleus, containing two protons and two neutrons. Its ground-state spin and isospin are zero. A quantized cubic four-Skyrmion supplies a corresponding nuclear state in the soliton description.

The bound atomic nucleus containing one proton and one neutron. Its ground-state spin is one and its isospin is zero. The appropriately quantized toroidal two-Skyrmion models these quantum numbers.

The positive energy needed to separate a bound atomic nucleus into its constituent protons and neutrons. It is the mass defect times $c^2$. In a Skyrmion model of a nucleus, both separated nucleon masses and the multi-soliton state require a consistent quantization and calibration.

The study of atomic nuclei, their structure, reactions and interactions. Nuclear forces between nucleons and nuclear binding energies connect it to the low-energy consequences of Quantum chromodynamics.

A charge-$A$ multi-Skyrmion provides an intrinsic field configuration for an atomic nucleus with mass number $A$. Its spatial and isospin collective coordinates must be quantized, with Finkelstein-Rubinstein constraints, before assigning physical nuclear states. A classical intrinsic shape is distinct from rotationally invariant observables in a spin-zero state.