Elements are atoms, atoms are elements. Elements are not larger objects made up of smaller things (atoms). Elements are specific species' atoms, which have a specific atomic mass which gives rise to...
Rust (in its "regular" red form) is an iron oxide called iron(III) oxide. It's formula is Fe2O3, and we call it ferric oxide or hematite. And that's different from iron (II) oxide FeO, or iron...