This element was discovered by J. de Marignac in Geneva, Switzerland, in 1878. The name comes from the Swedish town Ytterby.

Ionization energies
YbI 6.2 eV, YbII 12.2 eV, YbIII 25.0 eV.

Absorption lines of Ybl

Table 1. Equivalent widths of Y6I 3988 M.2-resonance line

Group V

S 0.018
K5 0.077

Absorption lines of YbII
In the sun the equivalent width of Yb II 3694 (M.1 resonance line) is 0.067.

Behavior in non-normal stars
Yb II was detached in at least one star of the Cr-Eu-Sr subgroup of Ap stars by Adelman et al. (1979).

Buscombe and Merrill (1952) found YbI in one S-type star.

Yb occurs in seven stable isotopic forms,namely Yb 168,170,171,172,173,174 and 176, and it also has nine short-lived isotopes and isomers. The stable isotopes occur in the solar system with frequencies 0.1%, 3%, 14%, 22%, 16%, 32% and 13% respectively.

Four isotopes - Yb 171, 172, 173 and 174 - can be produced by either the r process or the s process. Yb168 is a pure p, Yb170 a pure s and Yb176 a pure r process product.

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