Concept: Atomic weight is the average mass of an atom of an element compared to 121 the mass of a carbon-12 atom.Explanation:Nitrogen is element 7 on the periodic table.Its most common isotope is nitrogen-14, which contains 7 protons and 7 neutrons.The total number of protons and neutrons gives an approximate atomic weight of 7+7=14.The precise atomic weight of nitrogen is about 14.01, usually rounded to 14.From the given options, the correct value is 14.Answer: C. 14