  Review of the history of solar system elemental abundances with a new
assessment of elemental and isotopic abundances from CI-chondrites and solar
data. Solar elemental abundances, or solar system elemental abundances refer to
the complement of chemical elements in the entire solar system. The sun
contains more than 99-percent of the mass in the solar system and therefore the
composition of the sun is a good proxy for the composition of the overall solar
system. The solar system composition can be taken as the overall composition of
the molecular cloud within the interstellar medium from which the solar system
formed 4.567 billion years ago. Active research areas in astronomy and
cosmochemistry model collapse of a molecular cloud of solar composition into a
star with a planetary system, and the physical and chemical fractionation of
the elements during planetary formation and differentiation. The solar system
composition is the initial composition from which all solar system objects (the
sun, terrestrial planets, gas giant planets, planetary satellites and moons,
asteroids, Kuiper-belt objects, and comets) were derived. (Abstract truncated).
