The Nobel Prize in Chemistry 1934 was awarded to Harold C. Urey "for his discovery of heavy hydrogen".
 

Harold C. Urey attacked the problem of finding out whether it might be possible to discover an isotope of the simplest of all the elements, viz. hydrogen. As the atomic weight of hydrogen is approximately equal to 1, and as the atomic weights of the isotopes must differ by whole numbers, it follows that the nearest to ordinary hydrogen of any hydrogen isotopes there may be, must have an atomic weight of approximately 2, consequently double (100% more than) that of the hydrogen hitherto known. Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6,400 of hydrogen (~156.25 ppm).