Each dot represents an electron. Since the atomic number of oxygen is 8, it will have 8 protons in the nucleus. An atom of oxygen is neutral and so will have 8 electrons. Two electrons will fill ...

All oxygen atoms have 8 protons and all sodium ... Note that you can work out the number of neutrons by subtracting the atomic number from the mass number. In this example, it is 35 – 17 ...

Since this atom has a total of eight electrons, it also has eight protons. The atom with eight protons in its nucleus (atomic number 8) is oxygen. Each energy level holds a certain number of electrons ...