Table 1. Atomic masses and percent natural abundance of isotopes of elements relevant to organic compounds.
| Element | Isotope | Mass (abundance) | Isotope | Mass (abundance) | Isotope | Mass (abundance) |
| Carbon | 12C | 12.00000 (98.89) | 13C | 13.00335 (1.11) | ivory | ivory |
| Hydrogen | 1H | 1.007825 (99.985) | 2H | 2.01410 (0.015) | ivory | ivory |
| Nitrogen | 14N | 14.00307 (99.63) | 15N | 15.00011 (0.37) | ivory | ivory |
| Oxygen | 16O | 15.99491 (99.759) | 17O | 16.99914 (0.037) | 18O | 17.99916 (0.204) |
| Fluorine | 19F | 18.99840 (100) | ivory | ivory | ivory | ivory |
| Silicon | 28Si | 27.97693 (92.21) | 29Si | 28.97649 (4.70) | 30Si | 29.97376 (3.09) |
| Phosphorous | 31P | 30.97376 (100) | ivory | ivory | ivoryivory | ivory |
| Sulfur | 32S | 31.97207 (95.0) | 33S | 32.97146 (0.76) | 34S | 33.96786 (4.22) |
| Chlorine | 35Cl | 34.96885 (75.53) | 37Cl | 36.96590 (24.47) | ivory | ivory |
| Bromine | 79Br | 78.9183 (50.54) | 81Br | 80.9163 (49.46) | ivory | ivory |
| Iodine | 127I | 126.9044 (100) | ivory | ivory | ivory | ivory |