what is the number at the end of an isotopes name?\no atomic number\no neutron number\no mass number\no…

Brief Explanations:

Isotopes are named with the element name followed by the mass number. For example, carbon - 14 is an isotope of carbon where 14 is the mass number. The mass number is the sum of protons and neutrons in the nucleus of an atom.

Answer:

C. mass number