Vitamin B12, also known as cyanocobalamin, is a water-soluble vitamin that is part of the B vitamin family. B vitamins help support adrenal function, help calm and maintain a healthy nervous system, and are necessary for key metabolic processes.
For each of the 80 stable elements, the number of the stable isotopes is given. Only 90 isotopes are expected to be perfectly stable, and an additional 163 are energetically unstable, but have never been observed to decay. Thus, 253 isotopes (nuclides) are stable by definition (including tantalum-180m, for which no decay has yet been observed).
The half-lives of the five unstable isotopes of carbon differ greatly. Whereas half of any starting quantity of carbon-16 decays to nitrogen-16 in three quarters of a second, the same reaction for carbon-14 decaying to nitrogen-14 takes nearly six thousand years. Even so, carbon-14 is not a stable isotope, and will disappear in time. This slow decay of carbon-14 is the basis of a widely used dating method for archaeological materials. As long as any organism is alive, its carbon atoms are being exchanged continuously with the atmosphere.