- Geological specimens are known in which
the element has an isotopic composition outside the limits for normal
material. The difference between the atomic weight of the element in
such specimens and that given in the Table may exceed the stated
uncertainty.
- Range in isotopic composition of normal
terrestrial material prevents a more precise value being given; the
tabulated value should be applicable to any normal material.
- Modified isotopic compositions may be
found in commercially available material because it has been subject
to an undisclosed or inadvertant isotopic fractionation. Substantial
deviations in atomic weight of the element from that given in the
Table can occur.
- Commercially available Li materials have
atomic weights that range between 6.939 and 6.996; if a more accurate
value is required, it must be determined for the specific material
[range quoted for 1995 table 6.94 and 6.99].
- Element has no stable nuclides. The
value enclosed in brackets, e.g. [209], indicates the mass number of
the longest-lived isotope of the element. However three such elements
(Th, Pa, and U) do have a characteristic terrestrial isotopic
composition, and for these an atomic weight is tabulated.
- The names and symbols for elements
110-118 are under review. The temporary system recommended by J Chatt,
Pure Appl. Chem., 51, 381-384 (1979) is used above. The
names of elements 101-109 were agreed in 1997 (See Pure Appl. Chem.,
1997, 69, 2471-2473).
- The 2001 review agreed the following
changes zinc 65.39(2) to 65.409(4), krypton 83.80(1) to 83.798(2),
molybdenum 95.94(1) to 95.94(2) and dysprosium 162.50(3) to
162.500(1).
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