# How many neutrons in the iron nucleus?

""^56Fe is approx. 95% abundant. Because it is an iron isotope, we know that there are 26 protons in the element's nucleus (how do we know this?). Because it is the ""^56Fe isotope, there must be $56 - 26 = 30 \text{ neutrons}$ in this nucleus.
And thus there are $26 + 30$ nucleons, massive nuclear particles present in the nucleus. Capisce?