How do scientists determine the number of neutrons in an isotope of an atom?

A. They find the number of protons.

B. They divide the atomic mass by two.

C. They add the number of electrons and protons.

D. They subtract the atomic number from the atomic mass.

Scientists can calculate the number of neutrons by subtracting the atomic number from the atomic mass. The atomic number of an element is the number of protons which can be found in the nucleus of the element's atoms. The atomic mass of an element is the product of protons plus neutrons. The number of neutrons is not always equal to the number of protons. By subtracting the atomic number from the atomic mass, the difference will be how many neutrons are in the element's nucleus.