The alkaline-earth group atoms with the smallest radii are located higher up in the group. Here's why:

* Atomic Radius Trend: As you move down a group in the periodic table, the atomic radius increases. This is because you're adding more electron shells, which makes the atom larger.

* Alkaline-Earth Metals: The alkaline-earth metals (Group 2) are all located in the s-block of the periodic table. They have two valence electrons.

Therefore, the smallest alkaline-earth metal atom is beryllium (Be).

Here's the order of increasing atomic radius for the alkaline-earth metals:

* Beryllium (Be)

* Magnesium (Mg)

* Calcium (Ca)

* Strontium (Sr)

* Barium (Ba)

* Radium (Ra)