* Smaller atomic size: Oxygen has a smaller atomic radius than sulfur. This means the electrons in oxygen's outer shell are closer to the nucleus, experiencing a stronger attraction.
* Higher effective nuclear charge: The effective nuclear charge (the net positive charge experienced by an electron) is greater for oxygen than for sulfur. This is because oxygen has a higher nuclear charge (more protons) and fewer inner electrons shielding the outer electrons.
* Higher electron affinity: Oxygen has a higher electron affinity than sulfur, meaning it releases more energy when it gains an electron. This indicates a stronger attraction for electrons.
In summary: Oxygen's smaller size, greater effective nuclear charge, and higher electron affinity all contribute to its greater electronegativity compared to sulfur.
