The ion I3^- is known as the triiodide ion, which consists of three iodine atoms bonded together. It is commonly found in solutions, particularly in the presence of iodine and iodide ions. The triiodide ion is often used in various chemical applications, including as a reagent in analytical chemistry. In solution, I3^- appears as a deep brown color, which is a characteristic feature of the ion. It plays a significant role in the iodine chemistry and is important in biological systems, such as in the synthesis of thyroid hormones. The triiodide ion can also form complexes with other molecules, enhancing its utility in different chemical processes.