There are three naturally occurring isotopes of carbon on Earth: 99% of the carbon is carbon-12, 1% is carbon-13, and carbon-14 occurs in trace amounts, e.g. making up as much as 1 part per trillion (0.0000000001%) of the carbon in the atmosphere. The half-life of carbon-14 is 5,730±40 years. It decays into nitrogen-14 through beta decay.[3] The activity of the modern radiocarbon standard[4] is about 14 disintegrations per minute (dpm) per gram carbon.[5]
The atomic mass of carbon-14 is about 14.003241 amu. The different isotopes of carbon do not differ appreciably in their chemical properties. This is used in chemical research in a technique called carbon labeling: some carbon-12 atoms of a given compound are replaced with carbon-14 atoms (or some carbon-13 atoms) in order to trace them along chemical reactions involving the given compound.
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Subject: There are three naturally occurring isotopes 
Sun Dec 26, 2010 1:16 pm
