Answer
Boron
Work Step by Step
Each chlorine atom will contribute a single bond, so the central atom must have three valence electrons. Thus, we must pick a group 3 element, such as Boron.
You can help us out by revising, improving and updating this answer.
Update this answerAfter 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.