Final answer:
Atomic Number refers to the number of protons in an atom's nucleus and defines the element. Mass Number is the sum of protons and neutrons in an atom's nucleus. Atomic Mass, unlike mass number, is a weighted average of the masses of an atom's isotopes.
Step-by-step explanation:
The Atomic Number and Mass Number of an element are both important properties in Chemistry. The Atomic Number represents the number of protons in an atom's nucleus and defines the element. The Mass Number is the sum of protons and neutrons in the nucleus of an atom.
On the other hand, the Atomic Mass is slightly more complicated. It is the weighted average of isotopes of an element, considering both the mass of each isotope and the relative abundance of each isotope in nature. Hence, it's a decimal number. So, while the Mass Number is a whole number representing the number of particles in an atom's nucleus, the Atomic Mass is an average number representing the weighted average mass of a variety of isotopes.
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