The number of electrons in an atom is determined by its atomic number. Neon's atomic number is 10, which means that all neon atoms have 10 electrons. The difference between neon-20 and neon-22 is the number of neutrons. Neon-20 has 10 neutrons, while neon-22 has 12 neutrons. This difference in the number of neutrons does not affect the number of electrons in the atom.