* Sulfur's Electron Configuration: Sulfur (S) has an atomic number of 16, meaning it has 16 protons and 16 electrons. Its electron configuration is 1s²2s²2p⁶3s²3p⁴.

* Noble Gas Configuration: The nearest noble gas to sulfur is Argon (Ar), which has an electron configuration of 1s²2s²2p⁶3s²3p⁶.

* Gaining Electrons: To achieve the same electron configuration as argon, sulfur needs to gain two more electrons. This would fill its 3p orbital and give it a total of 18 electrons.

Therefore, a sulfide ion (S²⁻) gains two electrons to achieve a noble gas configuration.