4. What information does the atomic number of an element give us?

Answer: It gives us the identity of the element as well as the number of protons.

Explanation:

Because the number of protons is specific for each element, we can determine what element we are looking at just by the atomic number. For example the element with the atomic number of 1 is Hydrogen, atomic number of 2 is Helium, atomic number of 3 is Lithium and so forth.