Neon-20 has 10 Protons
Neon-21 has 11 Protons
Neon-22 has 12 Protons.
"For neon, which has 10 protons, the mass numbers of the three different naturally occurring isotopes are 20, 21, and 22, corresponding to 10, 11, and 12 neutrons, respectively. Percent means "per hundred." 90.48% means that 90.48 atoms out of 100 are the isotope with 10 neutrons."
