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).
Some isotopes are radioactive because their neutron/proton ratios are too large or too small. Explanation: The neutron/proton ratio (#n//p#) of a nucleus determines its stability. If #n//p# is too large or too small, the nucleus is unstable. It decays to form a more stable nucleus. The greater #n//p# value of carbon-14 is too large for a carbon atom. This makes the nucleus unstable.