ABSTRACT
The definitions of elements and isotopes were presented in sections 5.1 and 5.2. Elements are defined by the number of protons in the nucleus of their atoms. Hydrogen has one proton and oxygen has eight protons. Isotopes are defined as variations of a given element, differing from each other by the number of neutrons. As presented in section 5.2, the hydrogen isotopes are
1H-common hydrogen; 1 proton 2H-deuterium (also written D); 1 proton+1 neutron 3H-tritium (also written T); 1 proton+2 neutrons Tritium is radioactive and will be discussed in Chapter 10; common hydrogen
and deuterium are stable. Oxygen has the following isotopes: 16O-common oxygen; 8 protons+8 neutrons 17O-heavy (very rare) oxygen; 8 protons+9 neutrons 18O-heavy oxygen; 8 protons+10 neutrons Water is composed of hydrogen and oxygen, so it occurs with different
9.2 Units of Isotopic Composition of Water
The isotopic composition of water is expressed in comparison to the isotopic composition of ocean water. For this purpose an internationally agreed upon sample of ocean water has been selected, called Standard Mean Ocean Water (SMOW) (Craig, 1961a, 1961b).
