The atomic number of an isotope is the number of protons it contains, whereas the mass number is the total mass of the nucleus, which is the combined number of protons and neutrons in the nucleus. To find the number of neutrons, you must therefore subtract the atomic number of the isotope from the mass number of the isotope. <span>In the above example, the atomic number is 8 and the mass number is 18. This isotope is known as O18. The number of neutrons in the isotope is: Mass number - Atomic number = Number of neutrons
In the population with a large number of individuals, the mutation would only have a small impact, while a population with only 18 individuals would result in a very large i off as the mutation would be in a greater percentage of the population.
