Answer: B). 7
Explanation: The atomic number of an element is the number protons that are present in the nucleus of an atom of the element while the atomic mass of an element is the mass of its nucleus which is equal to the sum of protons and neutrons in the nucleus of the atom.
Atomic mass= number of protons + number of neutrons
Atomic mass of nitrogen= 14
Atomic number of nitrogen= number of protons= 7
Therefore, number of neutrons of nitrogen= 14-7
Number of neutrons = 7