Final answer:
According to the octet rule, sulfide ions should have a charge of -2, as sulfur gains two electrons to fill its valence shell, resulting in a stable configuration.
Step-by-step explanation:
According to the octet rule, sulfide ions (S²-) conform to a stable electron configuration by gaining two electrons. Sulfur, with an atomic number of 16, possesses six electrons in its valence shell and seeks to achieve a full octet by acquiring two more electrons. This results in an ion with 18 electrons and 16 protons, creating a net charge of -2. The extra electrons outnumber the protons, establishing the 2- charge. The symbol for a sulfide ion is S²-, signifying its attainment of electron stability through the gain of two electrons, aligning with the octet rule and mimicking the noble gas configuration.