The S2- ion, the simplest sulfur anion and also known as sulfide, has an electron configuration of 1s2 2s2 2p6 3s2 3p6. A neutral atom of sulfur has 16 electrons, but the atom then gains an additional two electrons when it forms an ion, taking the total number of electrons to 18.
In S2-, sulfur forms a negative ion, also known as an anion, which means that it is necessary to add two ions to the original electron configuration of neutral sulfur.
Sulfide is a very strong base, which means that all solutions of sulfide in water are also basic because of hydrolysis. Due to the hydrolysis, all solutions of sulfide in water have a smell similar to rotten eggs. When sulfide is mixed with water, it takes on one proton from the H2O, which results in one molecule of SH- and one molecule of OH-. When sulfide is mixed with an acid, it forms H2S, known as hydrogen sulfide, and a metal salt.
Sulfide is found in many important metal ores, such as argentite, molybdenite, galena and cinnabar. Argentite is a silver sulfide, galena is a lead sulfide, cinnabar is a mercury sulfide and molybdenite is a molybdenum sulfide. Lead sulfite is often used in infrared lasers.