An atom bonds with another atom. what is the best classification for this reaction?

endothermic
chemical
nuclear
redox

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.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.