Halogens typically have a charge of -1 when they form ions. This is due to their electronic configuration and their tendency to gain one electron to achieve a stable octet, similar to the noble gases.
In the periodic table, halogens are found in Group 17. They include fluorine, chlorine, bromine, iodine, and astatine. Each of these elements has seven valence electrons and needs to gain one more to fill their outer shell. When a halogen gains an electron, it becomes a negatively charged ion, known as an anion. For example, when chlorine gains an electron, it becomes a chloride ion (Cl–).
In summary, halogens have a primary oxidation state of -1, which reflects their reactivity and tendency to form ionic bonds with metals by accepting electrons.