Summary:
- 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.