The difference between the atomic number and the mass number

 

Atomic mass or weight is the average mass of the protons, neutrons, and electrons in an element's atoms. Science Photo Library - ANDRZEJ WOJCICKI, Getty Images. Photo from:https://www.thoughtco.com/definition-of-atomic-mass-weight-604375

The atomic number of an atom is the number of protons in the nucleus of an atom. It is denoted by the symbol "Z" and determines the chemical properties of an element. In a neutral atom, the number of electrons is equal to the atomic number.

On the other hand, the mass number of an atom is the total number of protons and neutrons in the nucleus of an atom. It is denoted by the symbol "A". The mass number determines the isotopic identity of an element, as isotopes of the same element have the same atomic number but different mass numbers.

To summarize, the main difference between atomic number and mass number is that the atomic number is the number of protons in the nucleus, while the mass number is the total number of protons and neutrons in the nucleus.