This element was discovered by L. Nilson in Uppsala, Sweden in 1879. Its name comes from Scandia (Scandinavia).

Ionization energies
ScI 6.5 eV, ScII 12.8 eV, ScIII 24.8 eV, ScIV 73.5 eV, ScV 91.7eV, ScVI 111.1 eV, ScVII 138 eV.

Absorption lines of ScI

Table 1. Equivalent widths of ScI

  5671 (a12-resonance line)     5343(4)  

Group V III Ib III Ia

F5 0.010   0.014    
F8     0.021    
G0     0.027    
G2 0.015   0.028    
S 0.014        
G5     0.063    
G8   0.059 0.126    
K0   0.079      
K2   0.112 0.190    
K3   0.181 0.219    
K5 0.153   0.245    
M0   0.186   0.039  
M2         0.044
M2.5   0.208      
M3       0.030  
M4       0.042  

ScI (see for instance 5671) appears in mid-F-type stars and grows monotonically toward later types. From late G-type onwards, a positive luminosity effect is visible for supergiants.

Emission lines of Scl
The line at 3907(8) is seen in emission in long-period variables. It is probably excited by flurorescence Joy 1954).

Absorption lines of ScII

Table 2. Equivalent widths of ScII

  4246(7)     5031(23)  

Group V III Ib V Ib  

B9 0.042        
A0 0.062   0.05    
A1 0.06        
A2 0.09   0.114(Ia)    
A7 0.20        
F0 0.24   0.575(Ia)    
F2     0.500    
F4 0.20     0.050  
F5 0.20,0.21   0.39    
F6       0.052  
F8 0.17   0.48 0.056 0.422
G0 0.15,0.19        
G1 0.23     0.100  
G2 0.16     0.060  
S 0.171        
G5 0.20        
G9 0.16(IV]     0.012(IV]  
K0 0.176 0.200      
K5 0.21     0.240  

Table 3. Equivalent widths of ScII 5657(29)

Group V III Ib

G0     0.26
G2 0.07   0.23
S 0.064    
G5     0.19
G8     0.24
K0   0.099,0.123(III)  
K2   0.13 0.20
K3   0.12 0.22
K5     0.19
MO   0.11  
M2.5   0.12  

Sc II lines (see for instance 4246) appear in late B-type, grow toward F-type and remain practically constant thereafter. A strong positive luminosity effect is present. The line at 5657 exhibits the same behavior. ScII also has two rather strong red lines at 6211(2) and 6306(2), which characterize late type stars (Keenan 1957).

Figure 44

Figure 45

Emission lines of ScII
In T Tau stars (Joy 1945) the line at 4246 as well as other ScII lines appear in emission.

Emission lines of higher ionization stages
The line 4823 of [ScVII] was observed in at least one recurrent nova by Joy and Swings (1945).

Behavior in non-normal stars
ScII lines tend to be strong in Bp stars of the Hg-Mn subgroup. W(4246) averages about 0.040 (Kodaira and Takada 1978). In contrast, Sc II lines tend to be weak in Ap stars of the Cr-Eu-Sr subgroup (Adelman 1973b). They are also weak in Am stars, which fact was discovered by Bidelman and further explored by Conti (1965). The average W values are smaller by about a factor of two. It must be added, however, that there exist Am stars in which Sc is of normal strength and even some stars in which Sc is strong (Cowley 1991). In delta Del stars the Sc II lines are weak (Kurtz 1976). However, Sc seems to behave normally in stars intermediate between Am stars and A-type giants (Berthet 1990).

Sc II lines are weakened by factors up to ten in F-type HB stars with regard to normal stars of the same colors (Adelman and Hill 1987). Adelman and Philip (1992a) remark that this applies to HB stars in general. Sc lines are probably variable in the blue stragglers of an old open cluster (Mathys 1991).

Sc seems to behave in a manner parallel to that of Fe in metal-weak dwarfs (Magain 1989) and in globular cluster stars (Wheeler et al. 1989). In extreme halo dwarfs Zhao and Magain (1990) found Sc to be overabundant with respect to Fe.

Strong ScII absorption lines appear in the spectra of supernovae of class II (Branch 1990).

Sc has one stable isotope, Sc45, and 14 unstable isotopes and isomers.

Sc can be produced by explosive nucleosynthesis, by Ne burning or by nuclear statistical equilibrium.

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