Final answer:
The combination of all elements from each set into a new set, in chemistry, is called a combination reaction, where two or more reactants form a single new product such as sodium and chlorine forming sodium chloride.
Step-by-step explanation:
The process of combining all elements from each set into a new set is referred to as a combination reaction or synthesis in chemistry. In the context of mathematics and set theory, this process might be referred to as the formation of a union of the sets, or a Cartesian product, if all possible ordered pairs are considered. However, based on the details provided, if the term is being sought from a chemistry perspective, where two or more substances combine to form a single new substance, the correct term is indeed a combination reaction. An example provided is where the elements sodium and chlorine come together in a combination reaction to create sodium chloride, a new substance.