Question

Acommon isotope of Carbon has an atomic number of and a mass number of 13. How many neutrons are in A 6 an atom of this isotope?

Answer 1

There are necessarily `7` neutrons in the `""^13C` isotope.

Explanation:

All carbon nuclei contain 6 nuclear protons; i.e 6 positively charged, massive nuclear particles. Were there a different number than 6, then we could not call it a carbon isotope, i.e for the `C` nucleus, `Z=6`.

Most carbon nuclei also contain 6 neutrons, 6 massive, neutrally charged nuclear particles; i.e. the `""^12C` isotope. A few carbon nuclei contain 7 neutrons rather than 6 to give the `""^13C` isotope; the isotopic abundance is approx. 1.1%.

Chemists can now routinely take advantage of the magnetic properties of the `""^13C` isotope by means of `""^13C{""^1H}` `"NMR spectroscopy"`. This is a bit less sensitive than `""^1H` `"NMR spectroscopy"`, and a bit of a longer experiment, but it is a direct method of analysis, and characterization of a new organic molecule would routinely demand details of its `""^13C{""^1H}` `"NMR spectrum"`.