The formula would be NI$_3$ as there are 3 iodines for every nitrogen.
Work Step by Step
Nitrogen is further left on the table than is iodine, hence it is put first.
You can help us out by revising, improving and updating this answer.Update this answer
After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.