How is the atomic radius defined?

The atomic radius is defined as half the distance between the nuclei of two bonded atoms. When two atoms are bonded together, the atomic radii can be measured by determining the distance between their centers and then dividing that value in half, which gives a representative measure of how far the outermost electrons of one atom are from the nucleus of the other. This definition effectively captures the size of the atom within the context of how it interacts and forms bonds with other atoms.

This choice aligns with the concept of atomic radii being relevant during bonding situations, such as covalent bonds, where the atoms are close enough for their electron clouds to overlap, allowing a clear measurement of distance between them. Understanding atomic radius in this manner helps in comparing sizes of different elements and their tendencies to bond with one another.