Which of the following scientists gave the concept of atomic mass?

John Dalton gave the concept of atomic mass. He proposed that all matter is composed of tiny, indivisible particles called atoms. He was the first to suggest that every element has a unique type of atom characterized by a specific relative atomic mass. His concept of atomic mass was derived from his work on the Law of Multiple Proportions and the weights of elements that combine to form compounds. Dalton initially used the mass of a hydrogen atom as the standard for comparison, before the standard eventually shifted to Oxygen-16 and finally Carbon-12.