Noun
hydrogen-1 (uncountable)
Synonym for protium (most common isotope of hydrogen)
For hydrogen-1, the quantity is about 1/1836 (i.e. the electron-to-proton mass ratio). Source: Internet
Nearly all deuterium found in nature was produced in the Big Bang 13.8 billion years ago, as the basic or primordial ratio of hydrogen-1 (protium) to deuterium (about 26 atoms of deuterium per million hydrogen atoms) has its origin from that time. Source: Internet
The name refers to examination of protons as they occur in protium (hydrogen-1 atoms) in compounds, and does not imply that free protons exist in the compound being studied. Source: Internet
Thus deuterium accounts for approximately 0.0156% (or on a mass basis 0.0312%) of all the naturally occurring hydrogen in the oceans, while the most common isotope ( hydrogen-1 or protium) accounts for more than 99.98%. Source: Internet
For hydrogen-1, hydrogen-2 ( deuterium ), and hydrogen-3 ( tritium ) the constant must be slightly modified to use the reduced mass of the system, rather than simply the mass of the electron. Source: Internet
However, other astronomical bodies are found to have different ratios of deuterium to hydrogen-1. Source: Internet