Ionic radius

Radio in picometers of some neutral atoms (in grey), cationes (in red) and anions (in blue).

The ionic radius is the radius of a monatomic ion in an ionic crystalline structure. Even if they were well defined. In the case of ions, the distance between the atomic nuclei of anions and cations in a crystalline arrangement is considered to correspond to the sum of the ionic radii of the anion and the cation.

In the case of cations, the absence of one or several electrons decreases the electrical force of mutual repulsion between the remaining electrons, causing them to come closer to each other and to the positive nucleus of the atom, resulting in a smaller ionic radius that the atomic,

In the case of anions, the phenomenon is the opposite, the excess of negative electrical charge forces the electrons to move away from each other to restore the balance of electrical forces, so that the ionic radius is greater than atomic radius.