This assumes that the atom in question is a hard sphere, the radius of which varies on its ionization state. This is a gross simplification to prime the readers mind. Typically, a cation has a smaller ionic radius because of the loss of an electron and an anion has a a larger ionic radius because of the addition of an electron.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.