Protium the most common isotope of hydrogen consists of one proton and one electron. Unique among all stable isotopes it has no neutrons. (see diproton for a discussion of why others do not exist) Main article: Hydrogen atom 1H (atomic mass 1.007 825 032 241(94) Da) is the most common hydrogen isotope with an abundance of more than 99.98%.
Hydrogen is the most abundant chemical substance in the universe constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state. The most common isotope of hydrogen termed protium (name rarely used symbol 1 H) has one proton and no neutrons .
Isotopes of hydrogen – Wikipedia
Isotope – Wikipedia
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