Final answer:
A sulfur atom typically becomes a sulfide ion with a 2- charge when it gains two electrons, resulting in a negatively charged ion denoted as S²-. Oxidation numbers, such as +4 in SO₂, are different from ion charges and relate to electron sharing in compounds.
Step-by-step explanation:
When a sulfur (S) atom becomes an ion, it usually has a charge of 2-. This is because when sulfur (Z = 16), which belongs to group 16, gains two electrons, it results in an ion with 18 electrons and 16 protons, leading to a negative two charge. Therefore, the ion formed is referred to as a sulfide ion with a chemical symbol of S²-.
It's important to differentiate the charge of an ion from its oxidation state in compounds. In the compound SO₂, sulfur has an oxidation number of +4, but this does not imply a 4+ charge on the sulfur atom itself; it's simply a convention used in chemistry to track electrons during chemical reactions.
Furthermore, when sulfur reacts with almost all metals, the sulfide ion (S²-) with a 2- oxidation state is usually formed, highlighting its tendency to gain two electrons when forming ionic bonds.