Originally posted by KazetNagorra
It depends on what you mean by "comes in." That list is probably the list of naturally occurring isotopes. The other ones can be synthesized but are not stable long enough to be found in nature. Why are certain isotopes more stable than others? I'm not sure there is a straightforward answer to this (at least not for the specific case of, say, 97-ruthenium versus 96-ruthenium) - atomic nuclei aren't the simplest of systems.
They listed the natural abundance percentage for each, 3 and 4 digit accuracy and they added up to 100% so I take it from those numbers there is no natural 97 or 103. Like you say, it must have something to do with stability issues. Maybe way too radioactive, short half life, something like that.
Anyone else with an answer?
Found this on 'chemicool' site:
Isotopes: Ruthenium has 26 isotopes whose half-lives are known, with mass numbers from 90 to 115. Naturally occurring ruthenium is a mixture of seven isotopes and they are found in the percentages shown: 96Ru (5.5😵, 98Ru (1.9😵, 99Ru (12.8😵, 100Ru (12.6😵, 101Ru (17.1😵, 102Ru (31.6😵, and104Ru (18.6😵. Naturally, the most common isotope is 102Ru with an abundance of 31.6%.
26 isotopes! So these 7 are just the natural occurring ones. So there is a 97 and so forth.
The crazy face icons are RHP's way of showing the percent symbol it looks like.