The attraction between forming the cluster is called a chemical bond or valence bond. It may be defined as follows.
”The attractive force that holds two or more atoms together in a molecule or compound is called a chemical bond”.
Atom consists of positive nucleus and negative electrons. When two atoms come closer to each other for bond formation, the attractive force and repulsive force begin to operate between them. The attractive forces are between the electrons of one atom and the nucleus of the other atom while the repulsive forces become dominant, no chemical bond is formed.
If the attractive forces become dominate, a bond is formed. On the other hand, if repulsive forces become dominant, no chemical bond is formed.
When atom sharing or transfer of electrons between the participating atoms then thy become strong chemical bonding. You can also see this strong chemical bond in the physical environment around us like crystals, metals and diatomic gases etc. those element’s atoms share or transfer electron each other which dictate the structure and the bulk properties of matter.