Final answer:
When an iodine atom, which normally has 53 protons, gains an additional proton, it transitions to become a xenon atom, as xenon is the element with 54 protons.
Step-by-step explanation:
If an iodine atom gains one proton, it no longer remains an iodine atom because the number of protons defines the element's identity. Iodine typically has 53 protons, so if it gains one more, it will have 54 protons. This would then represent a different element on the periodic table, specifically xenon (Xe), which is the element with 54 protons and is known for being a noble gas.
An increase in the atomic number due to a gain in protons means that the identity of the atom has changed to that of the next higher element on the periodic table.