Question

The number at the end of an isotope’s name is the ____ number. A) Atomic B)neutron C)mass D)electron

Answer 1

 each isotope of a given element has a different mass number. For example, carbon-12, carbon-13 and carbon-14 are three isotopes of the element carbon with mass numbers 12, 13 and 14 

Answer 2

I think mass but don't hold it against me.