What does the atomic number of an atom tell you ?

Hello there!

The atomic number of an atom tells you an element's identity, and informs you of how many protons are present in the nucleus of the atom. 

For example;
Potassium is an element with the symbol "K" on the periodic table that belongs in the Alkali Metal group, and has an atomic number of 19. This means that Potassium has 19 protons. 

I hope this helps!

Since there is the same amount of agn03 in both silver chloride and silver nitrate they produce the same amount of moles. therefore silver chloride produces the same amount of silver nitrate, so your answer is 15.0 moles of silver nitrate. i hope this !

The correct answer is "hydrogen".