The size of atoms is important when trying to explain the behavior of atoms or compounds. One of the ways we can express the size of atoms is with the atomic radius. This data helps us understand why some molecules fit together and why other molecules have parts that get too crowded under certain conditions.
The atomic radius of atoms generally increases from top to bottom within a group. As the atomic number increases down a group, there is again an increase in the positive nuclear charge.
Atomic radius is determined as the distance between the nuclei of two identical atoms bonded together.
The atomic radius of atoms generally decreases from left to right across a period.
The atomic radius of atoms generally increases from top to bottom within a group.