You are probably thinking of the electron orbitals which describe the spatial distribution of where the electrons are located. Their characteristic length scale

You are probably thinking of the electron orbitals which describe the spatial distribution of where the electrons are located. Their characteristic length scale is thousands of times smaller than the wavelength of light, so there is absolutely no way of resolving this structure. From an optical perspective an atom simply looks like an infinitely small radiating dipole. The nucleus itself is again tens of thousands of times smaller than the orbitals. Due to this small size and very high resonance energies, nuclei don't interact with visible light at all.