Final answer:
From the photoelectron spectra, it can be inferred that element Y likely has a greater nuclear charge than element X. The photoelectron spectra can also give clues about ionization energy, isotope abundances, and electronegativity, but these require additional context regarding the elements' positions in the periodic table.
Step-by-step explanation:
The photoelectron spectra of neutral atoms of elements X and Y reveal several important properties. The nuclear charge and the ionization energy can be inferred through understanding atomic structure and periodic trends. As per the photoelectron spectra data, element Y may have a greater nuclear charge than element X because the ionization energy generally increases with an increase in nuclear charge. Additionally, ionization energy tends to decrease as the atomic radius increases, which implies that if element X has a greater ionization energy than Y, X might have a smaller radius and be positioned to the left of Y in the periodic table. Considering the additional information provided, isotope abundances can affect the spectra but without explicit splitting pattern details from X and Y, this determination cannot be confidently made. Lastly, electronegativity generally increases across a period and decreases down a group, so if element X had a greater electronegativity than Y, its ionization energy typically would also be higher, again this inference depends on the position within the periodic table.