If atomic weight and atomic mass are different, why does the periodic table list the atomic mass as if it was the atomic weight?

Question

I’m so confused with these two. I know they are different terms but the periodic table shows atomic mass when to my understanding it should be the atomic weight because it’s taking into account their isotopes

In: Chemistry

Answer 1

The weight listed is the average of all naturally occurring isotopes. For example, Chlorine and Bromine have an almost 50/50 split between their two naturally occurring isotopes, so the weight listed on the periodic table is pretty much in the middle of them.