Answer
Atomic weight is the average of all naturally occurring isotopes of an element.
Work Step by Step
This is a weighted average based on prevalence and atomic mass of each isotope and will not come out to a whole number.
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.