How many Protons, Neutrons and Electrons are there in an atom of Silicon, Si?

Using a copy of the periodic table, look up the Mass and Atomic numbers of Silicon. Mass number = 28; Atomic number = 14. The Atomic number is equivalent to the number of Protons in an atom, so there are 14 Protons present in Silicon. The Mass number is equal to the number of Protons plus the number of Neutrons in an atom, so by subtracting the Atomic number from the Mass number we can determine that there are 28 - 14 = 14 Neutrons in Silicon. In an uncharged atom, the number of Electrons equals the number of Protons, so there are 14 Electrons in an atom of Silicon.