1. General properties

Atomic masses

The atomic mass values given in table 1 take into account the modifications made in 1999 and 2001 by IUPAC (International Union of Pure and Applied Chemistry, Commission on Atomic Weights and Isotopic Abundances). They are based on the isotope 12 of carbon ( ¹² C = 12 exactly). The number in brackets at the end of the atomic mass value represents the uncertainty of the last figure. This uncertainty reflects not only the precision of the measurement, but also the fact that the atomic masses of many elements depend on their natural origin (difference in isotopic composition).

Energy of first ionization

The energy of first ionization is the energy...