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: | SO42- |
|---|---|
| monoisotopic m/z: | 47.97641 |
| average m/z: | 48.0318 |
| base peak: | 47.9764 |
| charge: | 2-, so the values above are m/z |
Pattern
| m/z | nucleons | relative / % | abundance |
|---|---|---|---|
| 47.9764 | 96 | 100.00 | 94.070 % |
| 48.9750 | 98 | 5.30 | 4.983 % |
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.