Chapter 3

Neutron number (N) = number of neutrons for an element (can vary from the number of protons. This is called isotopes) The atomic mass (A) = Z+N, Q: why not consider the electron mass as well? A unit of mass for atoms is called an atomic mass unit (amu) = 1/12 of the Carbon 12 (12C) isotope which is the most common isotope of carbon. Here A=12 ... ................
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