Transcript: Hi, this is Dr. B. Let's do the Lewis Structure for NI3, Nitrogen Triiodide. That's one of Dr. B.'s favorite chemicals: big explosion, nice purple cloud. So let's look on the periodic table.Nitrogen is in Group 5, sometimes called fifteen, so it has five valence electrons. And then for Iodine we have seven valence electrons but there's three of them so 5 + 21 = 26 total valence electrons. Let's put Nitrogen in the center.It is the least electronegative.o let's look on the periodic table. Nitrogen is in Group 5, sometimes called fifteen, so it has five valence electrons. And then for Iodine we have seven valence electrons but there's three of them so 5 + 21 = 26 total valence electrons. Let's put Nitrogen in the center. It is the least electronegative.