Mass Number
Mass number explained in an easy to understand way:
Imagine trying to make a perfect sandwich by balancing just the right amount of bread and filling. Similarly, the mass number of an atom is like this perfect sandwich, where the bread represents protons and the filling represents neutrons. Just as the sandwich's overall weight depends on the right combination of bread and filling, an atom's mass number is determined by the sum of its protons (bread) and neutrons (filling) in the nucleus.
Practice Version
Mass Number: The sum of neutrons and protons in an atoms nucleus. mass number. The mass number is the total count of protons and neutrons present in the nucleus of an atom.