Question

An isotope of iron has 28 neutrons. If the atomic mass of the isotope is 54, how many protons does it have?

Answer 1

If it is an iron isotope, then it has 26 protons, period.

Explanation:

The iron atom is characterized by an atomic number, `"Z=26`. That is every iron nucleus contains `26` protons, 26, massive, positively charged, nuclear particles, by definition.

Of course, the nucleus also contains 28 neutrons, 28 neutral, massive nuclear particles, to give the `""^54Fe` isotope, which is about 4% abundant, check on this.

The number of protons, the number of massive, positively charged, nuclear particles, ALWAYS defines the identity of the element.