Besides placement on the defines the atom of the element by defining the number of protons in the atom.
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 of the element.
Carbon – 6 protons + 6 neutrons = 12 amu Nitrogen – 7 protons + 7 neutrons = 14 amu
I hope this was helpful. SMARTERTEACHER