^ abcdefgh The isotopic composition of the element can vary in commercial materials, which can cause the atomic weight to deviate significantly from the given value.
^ abcdefghijklmno The isotopic composition varies in terrestrial material such that a more precise atomic weight can not be given.
^ The atomic weight of commercial Lithium can vary between 6.939 and 6.996—analysis of the specific material is necessary to find a more accurate value.
^ abcdefghijklmnopqrstuvwxyzaaabacadaeafagahaiaj The element does not have any stable nuclides, and a value in brackets, e.g. , indicates the mass number of the longest-lived isotope of the element or characteristic isotopic composition.
^ This element has not been discovered/synthesized.
Atomic Weights of the Elements 2001, Pure Appl. Chem. 75(8), 1107-1122, 2003. Retrieved June 30, 2005. Atomic weights of elements with atomic numbers from 1-109 taken from this source.
IUPAC Standard Atomic Weights Revised (2005).
WebElements Periodic Table. Retrieved June 30, 2005. Atomic weights of elements with atomic numbers 110-116 taken from this source.