The mass would be 28. The mass of an atom equals the number of neutrons and protons added together. In this case, they do not say the protons. But we must use our inside knowledge to know that the number of protons equals the number of electrons. Thus, your number of protons would be 13
Theory- <span>a supposition or a system of ideas intended to explain something, especially one based on general principles independent of the thing to be explained.
Scientific law- </span>a statement based on repeated experimental observations that describes some aspect of the universe.
