For abundance data, it is normal for the values to cover many order of magnitude. For this reason it is common to quote and display the data in logarithm form as well. These data reflect the average composition of the sun and are determined by non-trivial spectroscopic methods.
Units are parts per billion by weight.
Units ppb by weight Notes Data given in different sources vary somewhat, reflecting the difficulty in assessing these numbers. Values given here are estimates derived by a consensus and averaging process for data abstracted from references 1-4. The units used in WebElements for all abundance data are ppb by weight which means parts per billion by weight , that is mg tonne -3 or mg per 1000 kg. All abundance data are also presented as ppb by atoms, which means atoms of the element per billion atoms. The reason for rescaling all data is as follows.