An atom is the size of a plastic building block. The larger the size of atom lesser is the ionization energy. See The Electron Configuration Diagrams For Atoms Of The Elements Potassium Atom Electron Configuration Atom Diagram The size of these atoms is said to have an order. . Size of atoms Atoms have a radius of about 01 nm nanometres or 00000000001 metres 1 10-10 m. R R R0A1 3 R 0 A 1 3. Describe on Size of Atom. One possible answer to this question is an exact measurement. An atom is small but can be seen with just our eyes. Structure of an atom. This means that the size of the nucleus is smaller than 410 -14 m. Get an answer for describe how the size changes when an atom forms a cation and when an atom forms an anion and find homework help for other Science questions at eNotes. An atom is the smallest unit of ordinary matter that forms a chemical element. Where R 0 1210 -15 m. We all ...