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drhunny t1_jd0wicd wrote

Isotopes are nuclides with the same number of protons. C-12,. C-13, C-14 are on the "6 proton isotope". Isotones are nuclides that have the same number of neutrons. H-3 and He-4 are on the n=2 isotone. Similar to how places at the same atmospheric pressure are on an isobaric line.

Weirdly, "isobar" is also a term in nuclear physics where it means same number of total neutron plus protons. I think it comes from from "baryon" whereas in meteorology it comes from "barometer"

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Ridley_Himself t1_jd16gt8 wrote

I had thought it came from them having about the same atomic weight iso=same, bar=weight/heavy.

But then baryon has the same root.

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Hoihe t1_jd2cymj wrote

/u/drhunny within Mass Spectrometry, we also use "isobar" to refer to fragments that may share the same nominal mass.

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El_Sephiroth t1_jd1xjvp wrote

Bar = unit of pressure. Isobar = same pressure everywhere. Baryon does not have the same roots. It is then Isobaryon but when talking nuclear physics you can shorten it because you usually don't talk about pressure so Isobar.

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Ridley_Himself t1_jd5po6a wrote

Bar is a unit of pressure, but it is still derived from the Greek root barus, meaning heavy. So we get a few words from the root such as barometer, isobar, baryon (“heavy particle“), barium (due to the high density of barium minerals).

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