In an element…

The Number of Protons is...

The atomic number is the number of protons in an atom of an element.

The Number of Electrons is...

By definition, atoms have no overall electrical charge. That means that there must be a balance between the positively charged protons and the negatively charged electrons. Atoms must have equal numbers of protons and electrons

The Number of Neutrons is...

Mass Number = (Number of Protons) + (Number of Neutrons)

The mass number should be round of to the nearest whole number.

In Summary...

For any element:

Number of Protons = Atomic Number

Number of Electrons = Number of Protons = Atomic Number

Number of Neutrons = Mass Number - Atomic Number