This element was discovered by C. Hatchett in 1801 in London. Its first name was columbium, which alludes to Columbus, because the element was dis- covered in minerals brought from America. In 1846 H. Rose, a German chemist, proved that columbium is not identical to tantalum, as was believed at that time, and he proposed the name niobium, because Niobe was a daughter of Tantalus in Greek mythology. The name niobium was finally adopted in 1950.

Ionization energy
NbI 6.9 eV, NbII 14.3 eV, NbIII 25.0 eV.

Absorption lines of NbI

Table 1. Equivalent widths of NbII 4152(1)

Group V III

S 0.008  
K5 0.074  
M5   0.181

Absorption lines of NbII

Table 2. Equivalent widths of NbII

  3620(4) 4579(8)

Group V III

S 0.015  
K0   0.098

In view of the small number of data, one can only conclude that both NbI and NbII are present in late type stars.

Behavior in non-normal stars
Jaschek and Brandi (1972) detected NbI in one Ap star of the Cr-Eu-Sr subgroup. Cowley et al. (1974) detected NbII in another star of the same subgroup.

Nb I lines are strengthened in Ba stars, which leads to overabundances of one order of magnitude (Lambert 1985, Smith 1984). NbI lines are also strengthened in subgiant CH stars (Krishnaswamy and Sneden 1985).

Merrill (1947) detected NbI in one S-type star and Davis (1984) added some more stars with Nb I. This detection was confirmed by Wallerstein and Dominy (1988), who found a variety of Nb strengths, although in general it seems weaker in S-type than in M-type giants of the same temperature. Lambert (1989) found that Nb apparently goes with Tc; but there exists at least one exception to this rule. See also Vanture et al. (1991).

Nb has one stable isotope, Nb93, and 23 short-lived isotopes and isomers. The longest lived is Nb94 with a half life of 2 × 104 years, which can be used for radioactive dating.

Nb is only produced by the s process.

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