<page_title> Isotopes of iodine </page_title> <section_title> List of isotopes </section_title> <table> <cell> 131I <col_header> nuclide symbol </col_header> <col_header> excitation energy </col_header> </cell> <cell> 8.02070(11) d <col_header> half-life </col_header> </cell> </table>
Iodine-131 has a half-life of eight days.