<P> The mass number ( symbol A ) , also called atomic mass number or nucleon number , is the total number of protons and neutrons ( together known as nucleons ) in an atomic nucleus . It determines the atomic mass of atoms . Because protons and neutrons both are baryons , the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion . The mass number is different for each different isotope of a chemical element . This is not the same as the atomic number ( Z ) which denotes the number of protons in a nucleus , and thus uniquely identifies an element . Hence , the difference between the mass number and the atomic number gives the number of neutrons ( N ) in a given nucleus : N = A − Z . </P>
<P> The mass number ( symbol A ) , also called atomic mass number or nucleon number , is the total number of protons and neutrons ( together known as nucleons ) in an atomic nucleus . It determines the atomic mass of atoms . Because protons and neutrons both are baryons , the mass number A is identical with the baryon number B as of the nucleus as of the whole atom or ion . The mass number is different for each different isotope of a chemical element . This is not the same as the atomic number ( Z ) which denotes the number of protons in a nucleus , and thus uniquely identifies an element . Hence , the difference between the mass number and the atomic number gives the number of neutrons ( N ) in a given nucleus : N = A − Z . </P>
what does the mass number of an isotope represent
what does the mass number of an isotope represent
the total number of protons and neutrons ( together known as nucleons ) in an atomic nucleus
the total number of protons and neutrons ( together known as nucleons ) in an atomic nucleus