Of Sn or I, which element has the higher first ionization energy?
Iodine has a greater first ionization energy than tin.
Ionization energy is the energy required to remove an electron from an element.
The general trend for ionization energy is that it increases as we go up and right in the periodic table. Iodine is in the same row as tin, but it is more to the right.
The reason iodine has a higher first ionization energy is that iodine wants to gain an electron (to have the same electron configuration as Xe), not lose one. Tin is a metal, so its ions have a positive charge, and it would want to lose electrons anyway.
Iodine is also more electronegative than tin, so iodine wants to keep its electrons more than tin does. For this reason it would be harder to remove an electron from iodine than it would be for tin.