The chemical formula for the chloride ion is Cl–.
Chloride ion is formed when chlorine, a halogen in Group 17 of the periodic table, gains an electron. This gain of an electron gives it a negative charge, which is indicated by the superscript minus sign in the formula. Chloride ions are commonly found in nature, primarily in salt (sodium chloride), and play crucial roles in various biological processes and in maintaining osmotic balance in cells.