Period 5 element required by higher animals, which use it to synthesize thyroid hormones, which contain the element. Because of this function, radioisotopes of iodine are concentrated in the thyroid gland along with nonradioactive iodine. The radioisotope iodine-131, which has a high fission product yield, concentrates in the thyroid, and is one of the most carcinogenic of nuclear fission products. Xenon has no biological role, and is used as a general anaesthetic. Period 5 element A period 5 element is one of the chemical elements in the fifth row (or "period") of the periodic table of the elements. The periodic table is laid
History of the periodic table published his periodic table of the known elements, predicted new elements to help complete his table and corrected the atomic weights of some of the elements, Meyer published a virtually identical periodic table. Meyer and Mendeleev are considered by some historians of science to be the co-creators of the periodic table, but Mendeleev's accurate prediction of the qualities of undiscovered elements enables him to have the larger share of the credit. In 1864, the English chemist William Odling also drew up a table that was remarkably similar to the table produced by Mendeleev. Odling overcame the tellurium-iodine problem and even