  The terrestrial and gas-giant planets in our solar system may represent some
prototypes for planets around other stars; the exoplanets because most stars
have similar overall elemental abundances as our sun. The solar system planets
represent at least four chemical planet types, depending on the phases that
make them: Terrestrial-like planets made of rock (metal plus silicates),
Plutonian planets made of rock and ice, Neptunian giant planets of rocky, icy
with low H and He contents, and Jovian gas-giant planets of rocky, icy planets
with near-solar H and He contents. The planetary compositions are linked to the
chemical fractionation in the planetary accretion disks. Chemical tracers of
these fractionations are described. Many known exoplanets are gas-giant planets
with up to several Jupiter-masses and their atmospheric chemistry is compared
to that of brown dwarfs. Exoplanets in close orbits around their host stars may
resemble hot brown dwarfs (L-dwarfs). Planets receiving less radiation form
their host may compare more to the methane-rich T dwarfs. The cloud layers
resulting from condensation of oxides, metal, sulfides, and salts in these hot
and cool gas giant planets and their chemical tracers are described.
