An isotope of iron has 28 neutrons. If the atomic mass of the isotope is 54, how many protons does it have?
If it is an iron isotope, then it has 26 protons, period.
The iron atom is characterized by an atomic number,
Of course, the nucleus also contains 28 neutrons, 28 neutral, massive nuclear particles, to give the
The number of protons, the number of massive, positively charged, nuclear particles, ALWAYS defines the identity of the element.