Answer:
Electron affinity.
Step-by-step explanation:
An atom can be defined as the smallest unit comprising of matter that forms all chemical elements. Thus, atoms are basically the building blocks of matters and as such determines or defines the structure of a chemical element.
Generally, atoms are typically made up of three distinct particles and these are protons, neutrons and electrons.
Electron affinity can be defined as the ability of an atom of a chemical element to accept or accommodate an electron.
This ultimately implies that, electron affinity is the change in energy of a neutral atom of a chemical element when an electron is added to the atom to form negative ion, thus, a neutral atom gain electron.
In Chemistry, electrons can be defined as subatomic particles that are negatively charged and as such has a magnitude of -1.