How does ionic radius change down the alkaline-earth metal group?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors. — alkaline-earth metal Modern version of the periodic table of the elements (printable).

The ionic radii of the alkaline-earth metals increase steadily as you move down the group in the periodic table. This trend is a direct result of the increasing size of the inner electron cores as the principal quantum number of the outermost orbitals increases.1

The following table illustrates the increase in the radius of the +2 ions (measured in angstroms) from beryllium to radium:

| Element | Ionic Radius (+2 ion, Å) |
| :--- | :--- |
| Beryllium (Be) | 0.31 |
| Magnesium (Mg) | 0.65 |
| Calcium (Ca) | 0.99 |
| Strontium (Sr) | 1.13 |
| Barium (Ba) | 1.35 |
| Radium (Ra) | 1.48 |

This steady growth in ionic size influences various chemical properties, including the ability of these ions to coordinate with other molecules and the strength of their bonding to ligands.12