Stable isotopes of oxygen and hydrogen in water - in a nutshell 

Most people can easily give the chemical formula of water - H2O. However, it is worth noting that the two elements that make up the water molecule - hydrogen and oxygen - have different isotopic varieties. In addition to the most common water molecules containing two atoms of "ordinary" hydrogen (1H) and one atom of "ordinary" oxygen (16O), there are also other molecules in nature, although perhaps not in such quantity, containing heavier, because they contain more neutrons in the nucleus, varieties of these elements. These are, for example, molecules 1H2H16O, 1H218O, or finally 1H217O. Since it became possible to measure the content of a given type of isotopic molecule in water, the isotopic composition of water has become a subject of wide interest to scientists. The source of this interest was the intuition that subtle differences in the masses of individual molecules would affect their different behavior during the changes that water undergoes. It soon turned out that much can indeed be learned about the history of water from its isotopic composition.