- The most abundant isotope of hydrogen, having atomic mass 1.protium
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
Examples from the Web for hydrogen-1
An atom of lithium-7 plus an atom of hydrogen-1 yields two atoms of helium-4 and plenty of energy.Unwise Child
Gordon Randall Garrett