* Electronegativity: Oxygen is much more electronegative than sulfur. This means oxygen has a stronger pull on electrons. While the difference in electronegativity is not as large as in classic ionic compounds, it's still significant enough to lead to a polar covalent bond. This means the electrons are shared unequally, with oxygen having a slightly negative charge and sulfur having a slightly positive charge.
* Ion Formation: To form an ionic bond, one element needs to readily lose electrons (forming a positive ion) and the other needs to readily gain electrons (forming a negative ion). Sulfur and oxygen, while having differences in electronegativity, are both nonmetals and don't readily form ions in this way.
Examples:
* Sulfur dioxide (SO2): This molecule has two polar covalent bonds between sulfur and each oxygen atom.
* Sulfur trioxide (SO3): This molecule has three polar covalent bonds between sulfur and each oxygen atom.
In summary: While there's a difference in electronegativity between sulfur and oxygen, the resulting bond is a polar covalent bond, not an ionic bond.
