Atomic Masses and Abundances

The previous discussion has centered on how to obtain as much molecular mass and chemical structure information as possible from a given sample. However, there are many uses of mass spectrometry where precise isotope ratios are needed and total molecular mass information is unimportant. For accurate measurement of isotope ratio, the sample can be vaporized and then directed into a plasma torch. The sample can be a gas or a solution that is vaporized to form an aerosol, or it can be a solid that is vaporized to an aerosol by laser ablation. Whatever method is used to vaporize the sample, it is then swept into the flame of a plasma torch. Operating at temperatures of about 5000 K and containing large numbers of gas ions and electrons, the plasma completely fragments all substances into ionized atoms within a few milliseconds. The ionized atoms are then passed into a mass analyzer for measurement of their atomic mass and abundance of isotopes. Even intractable substances such as glass, ceramics, rock, and bone can be examined directly by this technique. 

Only two isotopes of boron (B) occur in nature their atomic masses and abundances are given in the following table. Complete the table by computing the relative atomic mass of B to four significant figures, taking the tabulated relative atomic mass of natural boron as 10.811. 

More than half of all the atoms in naturally occurring zirconium are °Zr. The other four stable isotopes of zirconium have the following relative atomic masses and abundances ... 

TABLE 1 5.5 RELATIVE ATOMIC MASS AND ABUNDANCE OF SEVERAL ELEMENTS... 

Calculations involving non-integer relative atomic masses and abundance of isotopes from given data, including mass spectra... 

ATOMIC MASSES AND ABUNDANCES OF SEVERAL NATURALLY OCCURRING ISOTOPES... 

Update of Atomic Masses and Abundances Section 8 Analytical Chemistry... 

Atomic mass unit (amu), 1-1 to 11,1-23 to 26 Atomic masses, 1-14 to 17,11-56 to 253 Atomic Masses and Abundances, 1-14 to 17 Atomic Radii of the Elements, 9-49 Atomic radius, rare earth elements, 4-127 to 132... 

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