Answer
The smallest orbit would be one whose circumference equaled one electron wavelength.
Work Step by Step
This is according to the de Broglie model, explained on pages 608-609.
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.