To achieve an octet of valence electrons, an iodine atom will become an ion with what charge?

 Anion with negative charge

Explanation: Iodine atom belongs to the Group 17 elements which are also known as Halogens.

The electronic configuration of the Iodine(I) =  [Kr] 4d10 5s2 5p5

Thus when it will gain one electron in order to complete its valence shell of electrons with 8 electrons, it will acquire a negative charge.

Thus it will become an anion, which is not so much ready to lose its electron.

                                          I(s) + e → I -(aq)

periodic trends is an atom that gets larger as the number of electronic shells increase, the radius of atoms increases as you go down a certain group in the periodic table of elements. in general, the size of an atom will decrease as you move from left to right of a certain period.