Ne contains 10 electrons and 10 neutrons, While Ar contains 18 protons and 22 neutrons.
Work Step by Step
Initially you look at the lower number to the left of the element's symbol, this will give you the number of protons (the atomic number) of the element. To obtain the number of neutrons we look at the total atomic mass, which is the number above and to the left of the elements symbol, and we subtract this from our number of protons. Since electrons have a negligible mass, the total atomic mass minus the number of protons will leave you with the total number of neutrons in an atom.