A Is for Atom is a 14-minute 1953 promotional animated short documentary film created by John Sutherland and sponsored by General Electric (GE). It is now in the public domain. The short explains what an atom is, how nuclear energy is released from certain kinds of atoms, the peacetime uses of nuclear power, and the by-products of nuclear fission. It is Sutherland's most-decorated film, having won numerous honors at film festivals.
You can stream A Is for Atom 1953 (1953) free and legally on OldReel, via the Internet Archive.
Yes — it is in the public domain and can be watched and shared freely.