The size of a sulfur atom is a bit tricky to define because atoms don't have a fixed, solid boundary like a marble. We usually talk about its atomic radius, which is the distance from the nucleus to the outermost electron shell.

Here are some ways to describe the size of a sulfur atom:

* Covalent radius: This is half the distance between the nuclei of two sulfur atoms when they are covalently bonded. The covalent radius of sulfur is 1.04 Angstroms.

* Van der Waals radius: This is half the distance between the nuclei of two sulfur atoms when they are not bonded, but simply close to each other. The Van der Waals radius of sulfur is 1.80 Angstroms.

To put these numbers in perspective, 1 Angstrom (Å) is 0.1 nanometers, or 100 picometers. So, a sulfur atom is about 100 picometers in diameter.

Keep in mind that these are just approximate measurements, and the actual size of a sulfur atom can vary depending on its chemical environment and the way it's measured.