Carbon-14 is special because it is continually being made by cosmic rays bombarding nitrogen atoms in the upper atmosphere. Nitrogen is the commonest gas in the atmosphere and its mass number is 14, the same as carbon-14’s. The difference is that carbon-14 has 6 protons and 8 neutrons, while nitrogen-14 has 7 protons and 7 neutrons (neutrons, remember, have near-enough the same mass as protons). Cosmic ray particles are capable of hitting a proton in a nitrogen nucleus and converting it to a neutron. When this happens, the atom becomes carbon-14, carbon being one lower than nitrogen in the
...more
