Ionic+Radius

__**Ionic Size/Radius**__ The radius of an ion is related to the size of an ion (as in atomic radius), so the radius is based on a combination of the electrons in the ion, the orbitals, and nuclear charge. The distances between ions in ionic compounds also affect the sizes of ions. As a general rule, the radius of an ion increases as the principle quantum number gets larger. This tells us that with each column of a period, we can expect to see a bigger ion. In contrast, the radius decreases with an increasing nuclear charge. This makes sense because a greater nuclear charge attracts the electrons more strongly. As a result, the ion as a whole is drawn closer-creating a more compacted ion and, therefore, an ion with a smaller radius.

__**Ionic Radius of Cations**__ The ions formed on the left side of the periodic table create cations. When cations are formed, the outermost orbital is emptied. This is the result of a loss of electrons in order to become isoelectronic with the preceding noble gas. Since the ion has lost particles, the area of the ion decreases because there are less electrons to repel one another. This causes the ion to be more compacted, so the ionic radii of cations is smaller than the atomic radii of the respective atoms.

The ions formed on the right side of the periodic table create anions. This is the case because the atoms gain electrons in order to become isoelectronic with their succeeding noble gases. Since the ion has gained particles, the area of the ion increases because it must make room for the extra electrons that repel themselves. This spreads out the particles of the ion, so the ionic radii of anions is larger than the atomic radii of the respective atoms.
 * __Ionic Radius of Anions__**

This table shows the trend of ionic radii in the periodic table. We can see that the ionic radii of cations are smaller than their parent atoms, and that the ionic radii of anions are larger than their parent atoms.

Sources: __Chemistry: The Central Science__   