It would be atomic masses of the same atoms, and that atoms will be isotopes.
Answer:
A. Modern atomic theory is, of course, a little more involved than Dalton's theory but the essence of Dalton's theory remains valid. ... Also, there are different kinds of atoms (differing by their masses) within an element that are known as "isotopes", but isotopes of an element have the same chemical properties.
B. The explanation becomes a scientific theory. In everyday language a theory means a hunch or speculation. Not so in science. In science, the word theory refers to a comprehensive explanation of an important feature of nature supported by facts gathered over time.
