Question

How is the mass number calculated for an element?

A. The difference between the mass and the protons
B. There is no calculation. C. The product of neutrons and protons D. The sum of protons and neutrons

Answer 1

Together, the number of protons and the number of neutrons determine an element's mass number.

Answer 2

Together, the number of protons and the number of neutrons determine an element's mass number. Since an element's isotopes have slightly different mass numbers, the atomic mass is calculated by obtaining the mean of the mass numbers for its isotopes