* Electron Configuration: Sulfur has 16 electrons, with the following electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁴. This means its outermost shell (the third shell) has 6 electrons, but it can hold up to 8 electrons for stability.

* Octet Rule: Atoms tend to gain, lose, or share electrons to achieve a stable octet (8 electrons) in their outermost shell.

* Ion Formation: Sulfur achieves a stable octet by gaining two electrons, making its electron configuration 1s² 2s² 2p⁶ 3s² 3p⁶.

* Anion: Since sulfur gains electrons, it becomes negatively charged. This results in the sulfide ion (S²⁻).

In summary:

Sulfur forms its ion (S²⁻) by gaining two electrons to achieve a stable octet in its outermost shell, making it an anion with a -2 charge.