What is the overall trend in atomic size as you move down a group?

As you move down a group in the periodic table, the overall trend in atomic size is that it increases. This occurs primarily because of the addition of electron shells. Each subsequent element in a group has an additional electron shell compared to the one above it. The increased number of shells results in a greater distance between the nucleus and the outermost electrons, which effectively increases the size of the atom.

Furthermore, even though the nuclear charge increases with more protons in the nucleus, the effect of increased distance due to additional electron shells outweighs the nuclear attraction experienced by the outermost electrons. Additionally, there is increased electron-electron repulsion among the electrons in the outer shells, which also contributes to the larger atomic size as you descend a group. This understanding is critical for predicting the behavior of elements within a group, influencing properties such as reactivity and bond formation.