Isotope Pattern
The distribution of molecular masses that the natural isotopic composition of the elements produces — the M, M+1, M+2 series a mass spectrum shows — together with the monoisotopic and average mass.
- You supply
- A chemical formula, in the same grammar every other page here uses. Whole atoms only: a pattern describes one molecule, so a fractional stoichiometry is refused rather than rounded. Write a charge into the formula (
SO4^2-,Na+) and every mass becomes m/z, electron mass included. - Reading it
- Abundances are relative to the tallest peak, which is not always the monoisotopic one — for tin or a polybrominated compound it is not. This is an exact combinatorial result, not a simulated spectrum: no resolution, no peak shape, no adducts and no fragmentation.
Worked examples: a nickel complex · dibromomethane · tin tetrachloride · a sulfate anion
Input
Results
| formula: | SnCl4 |
|---|---|
| monoisotopic mass: | 259.77761 |
| average mass: | 260.5219 |
| base peak: | 259.7753 |
Pattern
| mass | nucleons | relative / % | abundance |
|---|---|---|---|
| 251.7802 | 252 | 1.34 | 0.320 % |
| 253.7776 | 254 | 2.62 | 0.626 % |
| 255.7769 | 256 | 22.01 | 5.264 % |
| 256.7782 | 257 | 11.18 | 2.673 % |
| 257.7757 | 258 | 59.72 | 14.284 % |
| 258.7769 | 259 | 25.66 | 6.137 % |
| 259.7753 | 260 | 100.00 | 23.918 % |
| 260.7748 | 261 | 21.70 | 5.190 % |
| 261.7739 | 262 | 86.93 | 20.792 % |
| 262.7723 | 263 | 8.66 | 2.071 % |
| 263.7736 | 264 | 48.28 | 11.547 % |
| 264.7697 | 265 | 1.66 | 0.397 % |
| 265.7740 | 266 | 20.35 | 4.868 % |
| 267.7735 | 268 | 6.20 | 1.484 % |
| 269.7715 | 270 | 1.11 | 0.266 % |
These are the relative abundances that follow from the natural isotopic composition of the elements — an exact combinatorial result, not a simulated spectrum. There is no instrument here: no resolution, no peak shape, no adducts and no fragmentation. Combinations with the same number of nucleons are shown as one peak at their abundance-weighted mass, which is what an instrument of ordinary resolving power sees; at high resolution several of these would split. Abundances are relative to the tallest peak, which is not always the monoisotopic one.