The best classification of reaction in which an atom bonds with another atom is chemical reaction
Explanation
In a chemical reaction, reactants come into contact to each other.
Bond between atoms in the reactant are broken down and then rearrange to form new bonds which form product
For example of a chemical reaction is as below
N2 + 3H2 → 2NH3
N2 and H2 are atoms that come in to contact to each other to form NH3.
