1934 Nobel Prize in Chemistry
Reason for Award
for the discovery of heavy hydrogen (deuterium)
Laureates
United States of America
Explanation
Hydrogen is a very small and light atom with one proton in the center and one electron orbiting around it. However, on rare occasions there is a “heavy hydrogen” atom that has a neutron as well as a proton in the center. Harold Urey discovered this special kind of hydrogen in his experiments. Heavy hydrogen is only slightly heavier than ordinary hydrogen, but when many atoms come together, even water becomes heavier. Scientists can use it to study how stars make energy and to learn many new things about nature.
Related Keywords
deuterium
Deuterium is the mass-2 isotope of hydrogen containing one proton and one neutron. Its natural abundance is only about 0.015 %, making it a valuable tracer of chemical and cosmic evolution. Although chemically similar to protium, slight differences in bond energy and vibrational frequency create isotope effects useful for mechanistic studies. D–D fusion produces 3He and neutrons, attracting interest in energy research. Deuterium is also an essential isotopic label and a component of deuterated NMR solvents.
isotope
Isotopes are nuclides with the same atomic number but different mass numbers. The proton count remains constant, while varying neutron numbers change the mass. Isotopes behave chemically almost identically, yet mass differences create kinetic isotope effects. Stable isotopes serve as environmental tracers and in medical diagnostics, whereas radioactive isotopes underpin dating techniques and radiation sources. The discovery of deuterium accelerated isotopic chemistry, driving advances in mass spectrometry and spectroscopy.
mass spectrometry
Mass spectrometry separates ionized molecules or atoms according to their mass-to-charge ratio, revealing chemical composition. Foundations were laid by Thomson, Dempster, and Aston, leading to multiple isotope discoveries. In Urey’s work, detection of mass-2 ions corroborated deuterium’s presence. Modern FT-ICR and Orbitrap instruments reach sub-ppm mass accuracy, supporting studies from proteomics to interstellar dust analysis. Mass spectrometry is indispensable for isotope-ratio measurements in environmental and geochemical tracing.
heavy water
Heavy water is water in which hydrogen is replaced by deuterium (D₂O), giving it a density about 10 % greater than ordinary water. Because of its low neutron-absorption cross-section, it serves as a moderator and coolant in natural-uranium reactors. When incorporated into organisms, it alters metabolic rates and is used for isotopic labeling in life sciences. During World War II, heavy-water supplies became a strategic focus in nuclear development. Today it is also employed in neutron-scattering experiments to reduce solvent background.
nuclear fusion
Nuclear fusion is the reaction in which light nuclei merge to form heavier nuclei, releasing enormous energy. In the Sun, proton-proton chains dominate, while terrestrial research focuses on D-T and D-D reactions. Deuterium is the most accessible fuel candidate, typically enriched from seawater by electrolysis. High-temperature plasma confinement is pursued with tokamaks and inertial confinement schemes. Commercial fusion remains challenging, but steady deuterium supply and efficient fuel cycles are crucial.
Big Bang nucleosynthesis
Big Bang nucleosynthesis (BBN) refers to the production of light elements within the first three minutes of the universe. Models predict the abundances of protons, neutrons, deuterium, helium, and trace lithium, allowing estimation of the cosmic baryon density by comparing with observations. Deuterium is easily destroyed in stars, so its current abundance largely reflects its primordial value. Without Urey’s discovery, observational verification would have been difficult. BBN stands alongside the cosmic microwave background as a cornerstone test of early-universe physics.
cosmochemistry
Cosmochemistry studies the chemical composition and isotope ratios of meteorites, planetary atmospheres, and interstellar dust to unravel the formation history of the solar system and the galaxy. Building on his deuterium work, Urey pioneered isotopic analysis of extraterrestrial materials, including the hydrogen isotopic distribution in lunar samples. The D/H ratio helps estimate the origin of water and the contribution of comets to Earth. Modern sample-return missions such as Hayabusa2 and OSIRIS-REx employ high-resolution mass spectrometry for this purpose. Cosmochemistry is closely linked to planetary exploration and studies on the origin of life.
nuclear physics
Nuclear physics investigates the structure and reactions of atomic nuclei to understand the strong interaction. Deuterium, as the simplest bound two-nucleon system, serves as a benchmark for nuclear-force models and scattering experiments. Analyses of its binding energy, quark configuration, and tensor forces are crucial for testing theory with data. Without Urey’s discovery, such precise comparisons would have lacked a reference. Deuterium targets are used in electron-scattering and neutrino experiments, contributing to the determination of fundamental constants.