I am not sure what "elementary school" is but in the context of atoms I guess this is more or less 10-12 years old. I was 10 in 1980 and as far as I can rememb

I am not sure what "elementary school" is but in the context of atoms I guess this is more or less 10-12 years old. I was 10 in 1980 and as far as I can remember we were always taught about atoms as normal things, with electrons etc. No controversy (that was in France). I think nobody told us about the capacity to see them or not though.