* Iodine (I) and its electrons: Iodine has 53 electrons and is in Group 17 (also known as VIIA) of the periodic table, meaning it has 7 valence electrons (electrons in its outermost shell).

* Gaining an electron: When iodine gains one electron, it now has 54 electrons.

* Matching valence electrons: Elements in Group 18 (VIIIA) have 8 valence electrons.

* The answer: When iodine gains one electron, it will have the same number of valence electrons as an element in Group 18 (like xenon (Xe)).

Therefore, an iodine atom that gains an electron will have the same number of valence electrons as xenon.