126C

126C - This is an example of nuclear Notation. In this particular case, we see Carbon in it's most abundant form, with an atomic mass of 12.

The recipe for nuclear notation is as follows: In Superscript, the mass number of the isotope is written, represented as A. In Subscript, the atomic number, which is the number of protons is written, represented as Z. The chemical symbol of the element is represented as X.

Example: Carbon-14. Carbon-14 has a mass number of 14, i.e., the number of nucleons <-- represented as A. Since we know Carbon has an atomic number of 6, that is what Z represents in this case. So far we have 146, and the only thing we are missing is the Chemical symbol of the element, which is C <-- Carbon.

To go further in depth; if you encounter a nuclear equation, using the knowledge of nuclear notation, as well as the type(s) of radiation emitted(alpha, beta and gamma), one can find out the resulting nuclide and type of radiation.

Example: 23490Th --> ? + Beta

Here you use your knowledge of Beta decay, which is 0-1B, and then you enter that into the equation, resulting in: 23490Th --> ? + 0-1Beta. Thereafter, you have to remember to look at the arrow(-->) as an equal sign and do the math, revealing the unknown nuclide: 23490Th --> 23489Ac + 0-1B.