For any element: Number of Protons = Atomic Number
Number of Electrons = Number of Protons = Atomic Number
Number of Neutrons = Mass Number – Atomic Number
The atomic number is the number of protons in an atom of an element. In our example, krypton’s atomic number is 36. This tells us that an atom of krypton has 36 protons in its nucleus. Atoms must have equal numbers of protons and electrons. Example, an atom of krypton must contain 36 electrons since it contains 36 protons. The mass number is the total number of neutrons and protons within the atom. For neutral atoms, the electron number is the same as the atomic number.
To find the number of neutrons, you will need to subtract the atomic number from the atomic mass. Example: For boron = 11 (atomic mass) – 5 (atomic number) = 6 neutrons