However, because it has too many neutrons for the number of protons it contains, it is not a stable atom.
The ions produced are forced into a magnetic field where the different mass of the carbon isotopes causes a different deflection, allowing the quantity of each isotope to be measured.
This method is claimed to be more accurate than the older and slower method of counting the number of radioactive decay emissions from a quite large sample.
But in actual practice, we know neither the original ratios nor if the specimen has been contaminated and are forced to make what we hope are reasonable assumptions.
The tiny initial amount of C14, the relatively rapid rate of decay (the half-life of C14 is currently about 5700 years) and the ease with which samples can become contaminated make radiocarbon dating results for samples "older" than about 50,000 years effectively meaningless.
PROBLEMS WITH RADIOCARBON DATING During the last 30 years, a new method of determining C14/C12 ratios has been developed.
It uses accelerator mass spectrometry to determine the amounts of C14 and C12 in a small sample which is vaporised in the test.The nitrogen atom, which began with seven protons and seven neutrons, is left with only six protons and eight neutrons.As the number of protons decides the chemical nature of an atom, the atom now behaves like a carbon atom.It is the supposed accuracy of the new method that allows measurements sensitive enough to date objects claimed to be more than twenty or thirty thousand years old.A recent test by the British Science and Engineering Research Council has shown that the accuracy of the new technique is greatly overrated.As you might guess, radioactive carbon (C) is quite rare.