Yes, an increase in atomic number can have an effect on the ionic radius of an atom.
Ionic radius refers to the size of an ion, which is an atom or a group of atoms that has gained or lost electrons to become electrically charged. When an atom loses electrons to form a positive ion (cation), the ionic radius decreases compared to its neutral atom. This is because the loss of negatively charged electrons reduces the electron-electron repulsion, allowing the remaining electrons to be drawn closer to the nucleus, resulting in a smaller radius.
Conversely, when an atom gains electrons to form a negative ion (anion), the ionic radius increases compared to its neutral atom. The addition of extra electrons increases the electron-electron repulsion, causing the electron cloud to expand and resulting in a larger radius.
As you move across a period (horizontal row) in the periodic table from left to right, the atomic number increases. In general, the ionic radius of cations tends to decrease from left to right across a period because the increasing positive charge in the nucleus attracts the electrons more strongly, leading to a smaller size.
On the other hand, as you move down a group (vertical column) in the periodic table, the atomic number also increases. In this case, the ionic radius generally increases as you move down the group. This is because each successive element in a group has an additional energy level or electron shell, which results in a larger atomic size and, consequently, a larger ionic radius.
However, it is important to note that there can be exceptions and variations due to specific electron configurations and interactions between different elements.