Carbon is the lightest member of the IVA family of the periodic table, atomic number 6, electronic configuration 1s22s22p2. Its first ionization potential is 11.26V. Its naturally-occurring stable isotopes are of mass 12 (98.89%) and 13 (1.11%). C14 is produced by cosmic rays in the atmosphere at a constant rate, and decays to stable N14 by β- emission with a half life of about 5730 years. A living sample of wood, say, has the equilibrium amount of C14. When it dies, the radiocarbon decays steadily, and the ratio of C14 to C12 declines to half in 5730 years, and so on. By measuring this ratio, the time when the wood was living can be estimated.