The atom would have two neutrons.
Mass number = neutrons + protons
12 = neutrons + 10
neutrons = 12 – 10 = 2
This would be an atom of neon-12.
No known isotopes of neon have only two neutrons. The neon isotope with the fewest neutrons is neon-16, and it is extremely reactive with a half-life of only 9 × 10⁻²¹ s.
