# Is carbon 12 an isotope?

Isotope, one of two or more chemical atom groups with the same atomic number and location in the periodic table and almost identical chemical behavior but with different atomic masses and physical properties.

In 1961, the International Union of Chemists selected the most stable isotope of carbon (C-12 isotope) as standard for comparison of the atomic masses of various elements. The mass of C-12 isotope was taken as 12 atomic mass units. This means that the atoms of the carbon 12 are the only ones with a relative atomic mass which is exactly a whole number.

The formal definition of relative atomic mass A of an element on the 12C scale is given by

$A = frac{Average mass of an atom of the element(gm)}{1/12th mass of 1 atom of 12C (gm)}$

For the element carbon At = 12.0111. This is the average of the isotopes of carbon which have different relative atomic masses and abundances.