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The Atom
An atom is the smallest unit of matter, it is composed of a nucleus which contains protons and neutrons, as well as electrons(which occupy the orbitals surrounding the nucleus).
*Note that an atom is mostly made up of empty space
Charges of the sub-atomic particles:
Electron=Negative/(-)
Proton=Positive/(+)
Neutron=No charge/0
Mass of the sub-atomic particles(amu):
Electron=0 or 1/1000 (or 0.000549)
Proton=1
Neutron=1
The mass number of an atom is the total number of protons and neutrons in an atom. It is also called the Nucleon Number since the protons and neutrons are located inside the nucleus. It is also never smaller than the atomic number, always either the same or larger.
The atomic number is the total number of protons and neutrons in an atom, it is unique to each element/identifies the element. The atomic number also determines the chemical properties of that element, which determines where it lands inside the periodic table.
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