The symbol to identify a particular atom is shown to the left. The atomic number, Z, is the number of protons in the nucleus of the atom, for a particular element this is always the same.
The mass number, A, is the number of protons and neutrons in the nucleus, for a particular element this may vary. Neutrons and Protons are collectively known as Nucleons, so the Mass number tells us how many Nucleons there are in the nucleus of the atom.
thechemguys.blogspot.com
The mass number, A, is the number of protons and neutrons in the nucleus, for a particular element this may vary. Neutrons and Protons are collectively known as Nucleons, so the Mass number tells us how many Nucleons there are in the nucleus of the atom.
thechemguys.blogspot.com
Example: this is the element Helium, chemical symbol He. it has 2 protons and 2 Neutrons, meaning it has an Atomic number of 2 and a Mass number of 4. In Nuclear Physics, we are concerned with the properties of the Nucleus only.