What is the difference between mass number and atomic number?

While the mass number is the sum of the protons and neutrons in an atom, the atomic number is only the number of protons. read more

There is a difference between the meanings of the chemistry terms atomic mass and mass number. One is the average weight of an element and the other is the total number of nucleons in the atom's nucleus. read more

The difference is that one is a count of the protons in an element’s nucleus while the other is a count of both the protons and neutrons. Atomic mass, also atomic weight, is the total weight of an element. read more

The atomic number of an atom is the number of protons that resides in the nucleus, while the mass number is the number of protons and neutrons combined. The atomic number determines the type of element an atom, while the number of neutrons determines the isotope of the element. read more