Enter the atomic symbol, including mass number and atomic number, for iodine-127.

127_53 I

Explanation:

The mass number of iodine is 127. It is written as a superscript above the symbol of the element. The atomic number of the element is 53. It is written as a subscript below the symbol of the element.

The symbol of iodine is I. The symbol was obtained from its English name.

The method of writing the atomic symbol of iodine is shown in the answer.

"the periodic table is arranged in order of atomic number."