What does the atomic number tell us?
Carbon - Atomic Number 6 has 6 protons
Nitrogen - Atomic NUmber 7 has 7 protons.
The proton number and the neutron number combine to provide the atomic mass number of the element.
Carbon - 6 protons + 6 neutrons = 12 amu
Nitrogen - 7 protons + 7 neutrons = 14 amu
I hope this was helpful.