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actinide series
actinide series a series of radioactive metallic elements in Group 3 of the periodic table . Members of the series are often called actinides, although actinium (at. no. 89) is not always considered a member of the series. The series always includes the 14 elements with atomic numbers 90 through...
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transactinide elements
transactinide elements , in chemistry, elements with atomic numbers greater than that of lawrencium (at. no. 103), the last member of the actinide series. See transuranium elements .
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transition elements
transition elements or transition metals, in chemistry, group of elements characterized by the filling of an inner d electron orbital as atomic number increases. This includes the elements from titanium to copper, and those lying in the columns below them in the periodic table . Many of the ...
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fermium
fermium [for Enrico Fermi ], artificially produced radioactive chemical element; symbol Fm; at. no. 100; mass no. of most stable isotope 257; m.p. 1,527°C; b.p. and sp. gr. unknown; valence +2, +3. Fermium is a member of Group 3 of the periodic table . The physical properties of fermium are l...
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lawrencium
lawrencium artificially produced radioactive chemical element; symbol Lr; at. no. 103; mass number of most stable isotope 262; m.p. about 1,627°C; b.p. and sp. gr. unknown; valence +3. Lawrencium is the last member of the actinide series of elements found in Group 3 of the periodic table . L...
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mendelevium
mendelevium , artificially produced radioactive chemical element; symbol Md; at. no. 101; mass no. of most stable isotope 258; m.p. 827°C; b.p. and sp. gr. unknown; valence +1, +2, +3. Mendelevium is a metal of the actinide series in Group 3 of the periodic table . The ninth transuranium ele...
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neptunium
neptunium , radioactive chemical element; symbol Np; at. no. 93; at. wt. 237.0482; m.p. about 640°C; b.p. 3,902°C (estimated); sp. gr. 20.25 at 20°C; valence +3, +4, +5, or +6. Neptunium is a ductile, silvery radioactive metal. It is a member of the actinide series in Group 3 of the p...
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nobelium
nobelium , artificially produced radioactive chemical element; symbol No; at. no. 102; mass no. of most stable isotope 259; m.p. 827°C; b.p. and density unknown; valence +2, +3. It is a metal of the actinide series in Group 3 of the periodic table . Nobelium was the 10th transuranium element...
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rare-earth metals
rare-earth metals in chemistry, group of metals including those of the lanthanide series and actinide series , usually yttrium , sometimes scandium and thorium , and rarely zirconium . Promethium, which is not found in nature, is not usually considered a rare-earth metal. The metals usually...
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actinium
actinium [Gr.,=like a ray], radioactive chemical element; symbol Ac; at. no. 89; at. wt. 227.0278; m.p. about 1,050°C; b.p. 3,200°C±300°C; sp. gr. 10.07; valence +3. Actinium is a silver-white metal with a cubic crystalline structure. It is found with uranium minerals in pitchbl...
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