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lutetium
lutetium formerly lutecium , metallic chemical element; symbol Lu; atomic number 71; at. wt. 174.967; m.p. about 1,663°C; b.p. about 3,395°C; sp. gr. 9.835 at 25°C; valence +3. Lutetium is a silver-white metal that is relatively stable in air. One of the rare-earth metals , it is th...
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rubidium
rubidium , metallic chemical element; symbol Rb; at. no. 37; at. wt. 85.4678; m.p. 38.89°C; b.p. 686°C; sp. gr. 1.53 at 20°C; valence +1. Rubidium is a very soft silver-white metal. One of the alkali metals , it is directly below potassium in Group 1 of the periodic table . It is extre...
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holmium
holmium [Lat.,=Stockholm], metallic chemical element; symbol Ho; at. no. 67; at. wt. 164.9304; m.p. about 1,474°C; b.p. about 2,425°C; sp. gr. 8.78 at 25°C; valence +3. Holmium is a soft, malleable, lustrous, silvery metal of the lanthanide series in Group 3 of the periodic table . I...
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thulium
thulium [from Thule, an ancient name for Scandinavia], metallic chemical element; symbol Tm; at. no. 69; at. wt. 168.9342; m.p. about 1,545°C; b.p. 1,947°C; sp. gr. 9.3; valence +3. Thulium is a soft, malleable, ductile, lustrous silver-white metal. It is one of the rare-earth metals of...
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scandium
scandium , metallic chemical element; symbol Sc; at. no. 21; at. wt. 44.9559; m.p. 1,541°C; b.p. 2,831°C; sp. gr. 2.99 at 20°C; valence +3. Scandium is a soft silver-white metal. It is a member of Group 3 of the periodic table ; because of its chemical and physical properties, its scarc...
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terbium
terbium [from Ytterby, a village in Sweden], metallic chemical element; symbol Tb; at. no. 65; at. wt. 158.9254; m.p. 1,356°C; b.p. 3,123°C; sp. gr. about 8.25; valence +3 or +4. Terbium is a soft, malleable, ductile, silver-gray metal. It is one of the rare-earth metals of the lanthan...
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praseodymium
praseodymium [Gr., =green twin], metallic chemical element; symbol Pr; at. no. 59; at. wt. 140.9077; m.p. 931°C; b.p. 3,512°C; sp. gr. about 6.8; valence +3 or +4. Praseodymium is a soft, malleable, ductile, silver-yellow metal. It exhibits allotropy ; the α-form (hexagonal crystalli...
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neodymium
neodymium , metallic chemical element; symbol Nd; at. no. 60; at. wt. 144.24; m.p. about 1,021°C; b.p. about 3,068°C; sp. gr. 7.004 at 20°C; valence +3. Neodymium is a lustrous silver-yellow metal. It is one of the rare-earth metals in the lanthanide series of Group 3 of the periodi...
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lanthanum
lanthanum [Gr.,=to lie hidden], metallic chemical element; symbol La; at. no. 57; at. wt. 138.9055; m.p. about 920°C; b.p. about 3,460°C; sp. gr. 6.19 at 25°C; valence +3. Lanthanum is a soft, malleable, ductile, silver-white metal; at room temperature it has a hexagonal close-packed cr...
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dysprosium
dysprosium [Gr.,=hard to get at], metallic chemical element; symbol Dy; at. no. 66; at. wt. 162.50; m.p. 1,412°C; b.p. 2,562°C; sp. gr. 8.54 at 25°C; valence+3. Dysprosium is a lustrous silvery metal; it is very soft and can be cut with a knife. It is in Group 3 of the periodic table ...
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