| metals, actinoid | A series of radioactive elements from actinium, atomic number 89, to and including lawrencium, atomic number 103. They are the theoretical analogs of the rare earth metal series. (12 Dec 1998) |
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| actinoid | Having the form of rays; radiated, as an actinia. Origin: Gr, ray. Source: Websters Dictionary (01 Mar 1998) |
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| metals | Electropositive chemical elements characterised by ductility, malleability, luster, and conductance of heat and electricity. They can replace the hydrogen of an acid and form bases with hydroxyl radicals. (12 Dec 1998) |
| metals, alkali | Metals that constitute group ia in the periodic table. They are the most strongly electropositive of the metals. (12 Dec 1998) |
| metals, alkaline earth | Metals that constitute the group IIa in the periodic table. (12 Dec 1998) |
| metals, heavy | metals with high specific gravity, typically larger than 5. They have complex spectra, form coloured salts and double salts, have a low electrode potential, are mainly amphoteric, yield weak bases and weak acids, and are oxidizing or reducing agents (12 Dec 1998) |
| metals, light | Metals with low specific gravity, typically smaller than 5, characterised by a single valence (1, 2, or 3), a simple spectrum, strong electromotive force (positive), and colourless compounds. (12 Dec 1998) |
| metals, rare earth | Elements of group IIIb of the periodic table from lanthanum, atomic number 57, to and including lutetium, atomic number 71. (12 Dec 1998) |
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