What is a chemical element?
From a scientific standpoint, there is no difference.  Elements=Atoms=the 100 or so basic building blocks of chemistry.

This is purely conjecture, but I suspect that the term/concept "elements" pre-date "atoms" (at least atoms as we know them today).  I could see "elements" referring to the macroscopic description, e.g. a jar of carbon (graphite), but it may not have been realized back-in-the-day that these were aggregations of many carbon atoms.

"Atom" strikes me as quantum scale, and "Element" strikes me as something on the macroscopic scale, perhaps hearkening back to the pre-atomic days.  But really, there is no difference.