Changes that reorder atoms to form new molecules, such as the reaction between sodium and chlorine ions to form sodium chloride, are known as

A physical change doesnot change the chemical composition of elements or molecules involved. While a chemical change involves the formation of a new molecule or a compound from reacting species. This leads to an alteration in the chemical composition of the substance. Chemical changes influence both physical and chemical properties of the substances undergoing the change. In this type of change, atoms rearrange to form new compounds.

Therefore, the correct answer is Chemical change.