The Elements 1.5 Data 85
Table 2.1-12B(a) Elements of Group IIIB (CAS notation), or Group 3 (new IUPAC notation). Crystallographic properties
(see Table 2.1-12C for allotropic and high-pressure modifications)
Element name Scandium Yttrium Lanthanum Actinium
Chemical symbol Sc Y La Ac
Atomic number Z 21 39 57 89
Units Remarks
Modification α-Sc α-Y α-La
Crystal system, Bravais lattice hex hex hex
Structure type Mg Mg α-La
Lattice constant a 330.88 364.82 377.40 pm
Lattice constant c 526.80 573.18 1217.1 pm
Space group P6
3
/mmc P6
3
/mmc P6
3
/mmc
Schoenflies symbol D
4
6h
D
4
6h
D
4
6h
Strukturbericht type A3 A3 A3
Pearson symbol hP2 hP2 hP4
Number A of atoms per cell 2 2 4
Coordination number 12 6+6 12
Shortest interatomic distance, solid 166 364 pm
Table 2.1-12B(b) Elements of Group IIIB (CAS notation), or Group 3 (new IUPAC notation). Mechanical properties
Element name Scandium Yttrium Lanthanum Actinium
Chemical symbol Sc Y La Ac
Atomic number Z 21 39 57 89
Units Remarks
Density , solid 2.989 4.50 6.70 10.07 g/cm
3
Molar volume V
mol
15.04 19.89 22.60 cm
3
/mol
Surface tension, liquid 0.9 0.9 0.71 N/m
Coefficient of linear 10.0×10
−6
10.6×10
−6
4.9×10
−6
1/K
thermal expansion α
Sound velocity, solid, 2420 1540 m/s
transverse
Sound velocity, solid, 4280 2770 m/s
longitudinal
Compressibility κ 2.22 ×10
−5
2.62× 10
−5
3.96× 10
−5
1/MPa Volume
compressibility
Elastic modulus E 75.2 66.3 39.2 25
a
GPa
Shear modulus G 29.7 25.5 14.9 GPa
Poisson number µ 0.28 0.27 0.28
Elastic compliance s
11
12.5 15.4 51.7
b
1/TPa
Elastic compliance s
33
10.6 14.4 1/TPa
Elastic compliance s
44
36.1 41.1 55.7
b
1/TPa
Elastic compliance s
12
−4.3 −5.1 −19.2
b
1/TPa
Elastic compliance s
13
−2.2 −2.7 1/TPa
Elastic stiffness c
11
99.3 77.9 34.5
b
GPa
Elastic stiffness c
33
107 76.9 GPa
Elastic stiffness c
44
27.7 24.3 18.0
b
GPa
Elastic stiffness c
12
39.7 29.2 20.4
b
GPa
Elastic stiffness c
13
29.4 20 GPa
Tensile strength 256 250–380 MPa
Vickers hardness 350 40 491
a
Estimated.
b
For lanthanum in its metastable fcc phase at room temperature.
Part 2 1.5