Isotope
The number of protons a nucleus contains determines which element that atom belongs to. Nuclei containing the same number of protons always belong to the same element. If two nuclei of the same element have different numbers of neutrons they are called isotopes of one another. Although isotopes differ in mass, their chemical properties are almost identical.
Most elements have more than one naturally occuring isotope. The table below describes the naturally occuring isotopes of carbon and hydrogen as well as some other isotopes commonly used in NMR.
| Atom | Protons | Neutrons | Mass number | Abundance/% |
|---|---|---|---|---|
| 1H | 1 | 0 | 1 | 99.98 |
| 2H | 1 | 1 | 2 | 0.02 |
| 3H | 1 | 2 | 3 | <0.001 |
| 12C | 6 | 6 | 12 | 98.9 |
| 13C | 6 | 7 | 13 | 1.1 |
| 14N | 7 | 7 | 14 | 99.6 |
| 15N | 7 | 8 | 15 | 0.4 |
| 17O | 6 | 7 | 13 | 1.1 |
| 19F | 9 | 10 | 19 | 100 |
| 31P | 15 | 16 | 31 | 100 |
