The reaction of sodium and chlorine to form salt is best described as an

The reaction of sodium and chlorine to form salt has the following properties:

1 - It gives out (releases) heat. This means that it is an exothermal reaction

2 - A new compound is formed and the components of this compound cannot be separated by physical means. This means that a chemical change occurred.

Based on this:

The reaction of sodium and chlorine to form salt is best described as an exothermic chemical change reaction.