What does the covalent radius measure?

The covalent radius measures the distance between the nuclei of two bonded atoms in a covalent bond. It is defined as half the distance between the nuclei of two identical atoms that are bonded together. This radius provides insight into the size of the atoms involved in a bond and the spatial relationships in molecular structures. Understanding the covalent radius is crucial as it influences molecular geometry and the reactivity of different substances.

The other options focus on different aspects of atomic and molecular properties. The energy required to break a bond deals with bond strength rather than the distance between atoms. The mass of an atom pertains to its atomic weight and does not relate to bond distances. The charge of an electron is unrelated to covalent bonding, as it concerns the fundamental charge characteristics of subatomic particles rather than their spatial arrangements in molecules.