The element was known in pre-Columbian America. Ulloa discovered this element in 1735. The name is derived from the Spanish plata (silver).

Ionization energies
PtI 9.0 eV, PtII 18.6 eV, PtIII 29.0 eV.

Absorption lines of PtI
In the sun the equivalent width of PtI 3065(2) is 0.083.

Behavior in non-normal stars
PtI was detected by Brandi and Jaschek (1970) in several Ap stars of the Cr-Eu-Sr subgroup.

PtII lines were detected by Dworetsky (1969) in some Bp stars of the Hg-Mn subgroup. A typical value is W(4046) = 0.054. PtII was also detected by Cowley (1987) and by Fuhrmann (1989) through the ultimate line 1777(13) in several Ap stars of the Si and Cr-Eu-Sr subgroup.

Pt has six stable isotopes: Pt 190, 192, 194, 195,196 and 198, which occur in the solar system with frequencies of 0.01%, 0.8%, 33%, 34%, 25% and 7%. There exist also 26 unstable isotopes and isomers.

Pt 194, 195, 196 and 198 can only be produced by the r process, Pt192 only by the s process and Pt190 by the p process.

Published in "The Behavior of Chemical Elements in Stars", Carlos Jaschek and Mercedes Jaschek, 1995, Cambridge University Press.