Final answer:
The term defined as one-half the distance between the nuclei of identical atoms bonded together is the covalent radius, which helps in measuring atomic size in molecules.
Step-by-step explanation:
The term that may be defined as one-half the distance between the nuclei of identical atoms bonded together is the covalent radius. This is often used to determine the atomic size in covalently bonded diatomic molecules.
The radius for halogens, for example, increases down the group as the principal quantum number, n, increases, thereby indicating a larger atomic size for halogens with higher n.
It's important to note that different types of atomic radii can be defined, such as the van der Waals radius or the metallic radius, but for identical atoms bonded covalently, the covalent radius is the appropriate measure.