Sulfur (S):

* Element: Sulfur is a non-metal element found naturally in its elemental form.

* Appearance: It's a yellow, brittle solid.

* Structure: Sulfur atoms can form different structures, including rings and chains. In its most common form, it's a ring of 8 sulfur atoms (S₈).

* Reactivity: Relatively unreactive in its elemental form, but it can react with other elements to form compounds.

Sulfur Dioxide (SO₂):

* Compound: Sulfur dioxide is a compound formed by the combination of sulfur and oxygen.

* Appearance: It's a colorless gas with a pungent odor.

* Structure: It has a bent molecular structure, with a sulfur atom double-bonded to two oxygen atoms.

* Reactivity: More reactive than elemental sulfur. It dissolves in water to form sulfurous acid (H₂SO₃), making it acidic. It's a major air pollutant.

Key Differences:

* Composition: Sulfur is a pure element, while sulfur dioxide is a compound.

* Structure: Sulfur can exist in different structures, while sulfur dioxide has a specific bent structure.

* Reactivity: Elemental sulfur is less reactive than sulfur dioxide.

In summary: Sulfur and sulfur dioxide are distinct substances with different chemical compositions, structures, and reactivity.