• The atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.
  • Elements are different because of their atomic number.
  • The classification of elements by atomic number allows us to understand many properties of the atom and makes it possible to predict behaviors instead of just having to memorize everything.
  • If you have a cell phone in your name, nobody else in the world has that number.
  • Email addresses are different for each of us, which is a good thing since we can email almost anywhere.
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