The Three Isotopes of Hydrogen

The three isotopes of hydrogen are almost indistinguishable for most chemical purposes, but a mass Spectrometer can see them as three different entities of mass 1, 2, and 3 Da. Isotopes of other elements can also be distinguished. Mass spectrometry is important for its ability to separate the isotopes of elements. 

A few natural isotopes are radioactive. Of the three isotopes of hydrogen, only that of mass 3 (tritium) i.s radioactive. Radioactive isotopes can be examined by other instrumental means than mass spectrometry, but these other means cannot see the nonradioactive isotopes and are not as versatile as a mass Spectrometer. 

Isotopes are atoms with the same atomic number but different mass numbers. All isotopes of an element have the same number of electrons. Table 14.1 illustrates the three isotopes of hydrogen. 

TABLE 14.1 NUCLEAR COMPOSITION OF THE THREE ISOTOPES OF HYDROGEN... 

Isotopes are atoms of the same element with the same number of protons (same atomic number) but different number mass numbers (due to a different number of neutrons). Isotopes have identical chemical properties (the same reactivity) but different physical properties (i.e., some are radioactive, while others are stable). Consider the three isotopes of hydrogen in Table 2.1. 

In comparing the three isotopes of hydrogen, the order of priorities is ... 

The three isotopes of hydrogen have special names. 

The mass number for normal hydrogen atoms is 1 for deuterium, 2 and for tritium, 3. The composition of a nucleus is indicated by its nuclide symbol. This consists of the symbol for the element (E), with the atomic number (Z) written as a subscript at the lower left and the mass number (A) as a superscript at the upper left, By this system, the three isotopes of hydrogen are designated as H, H, and ]H. 

The three isotopes of hydrogen each have its own chemical symbol (H, D and T) whereas isotopes of other elements do not have special chemical symbols. Many elements have many isotopes but only relatively few of these are stable. A stable isoptope will not undergo radioactive decay. The nucleus of an unstable isotope on the other hand will undergo radioactive decay which means that the nucleus will transform into other isotopes or even other elements. In the following example we will look more at isotopes for the element uranium. 

It would be welcome if Fishbein s work on the early steps of the methylamine deamination would be continued by a stereochemical investigation of the dediazoniation proper by use of chiral methylamine, i. e., the compound in which the C-atom is stereospecifically substituted by the three isotopes of hydrogen, i. e., pro-tium, deuterium, and tritium. The first compounds with a chiral methyl group were (i )- and (S )-[2- H,2- H]acetic acid, synthesized by the groups of Cornforth and Arigoni in 1969 (Cornforth et al., and Liithy et al., respectively). ... 

II) The three isotopes of hydrogen iH (normal hydrogen or protium)... 

The three isotopes of hydrogen may be represented by the symbols H, iH, and ]H, indicating an atomic number of 1 and mass numbers of 1, 2, and 3, respectively. This method of representing atoms is called isotopic notation. The subscript (2) is the mass number atomic number the superscript (A) is the mass number, which is the sum of the number of protons and the number of neutrons in the nucleus. The hydrogen isotopes may also be referred to as hydrogen-1, hydrogen-2, and hydrogen-3. 

The three isotopes of hydrogen are represented as follows using this notation Jh, jH, and iH. When these symbols are not convenient to use, as in written or spoken references to the isotopes, the elemental name followed by the mass number is used. Thus, the three hydrogen isotopes are hydrogen-1, hydrogen-2, and hydrogen-3. These three isotopes have specific names protium (A = 1), deuterium (A = 2), and tritium (A = 3). 

Use of the three isotopes of hydrogen to fabricate chiral methyl groups for study of the stereochemistry of enzyme-catalysed reactions involving methyl groups is to be noted (Sections 1.2.2, 4.2 and 4.4). 

Many elements exist as a mixture of isotopes. Figure 2.14 shows the isotopes of carbon, chlorine and hydrogen as nuclide symbols. Isotopes of the same element all have the same element symbol and atomic number. Figure 2.15 shows the three isotopes of hydrogen as Bohr diagrams. 

Figure 2.15 The three isotopes of hydrogen protium, deuterium and tritium... 

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