The order of atoms in increasing radius: Na, Ca, Ba.
Work Step by Step
In the periodic table, there are two trends in bonding atomic radii: 1) From left to right across a period, the bonding atomic radii of the atoms tend to become smaller and smaller (due to the increasing effective nuclear charge). 2) From top to bottom across a group, the bonding atomic radii of the atoms tend to increase (due to the expansion of the principal quantum number n, giving the electrons more chance to be further from the nucleus) Ba and Ca are in the same group 2A. From top to bottom, the elements appear in the following order: Ca, Ba. That means the radius of Ba is greater than the radius of Ca. Na is in group 1A and period 3. Ca is in group 2A and period 4. From period 3 to period, we expect a greater increase in atomic radii than from group 2A to 1A. Which means the atomic radii, or the size of Ca is greater than Na. Overall, the order of atoms in increasing radius: Na, Ca, Ba.