Chemistry I / Atomic Models and Isotopes
Practice question · Numerical answer

An isotope has mass number A=56A = 56 and atomic number Z=26Z = 26. How many neutrons does its nucleus contain?

Hints
  1. The mass number counts protons and neutrons together.
  2. Neutrons = A minus Z.
Show the answer

30

Why

Neutrons =AZ=5626=30= A - Z = 56 - 26 = 30. This is iron-56, the most tightly bound nucleus per nucleon.

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