| 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, 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) |
| 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) |
| metaluetic | Synonym: metasyphilitic. Synonym: metasyphilitic. Synonym: parasyphilitic. Origin: meta-+ L. Lues, pestilence (05 Mar 2000) |
| metamer | <chemistry> Any one of several metameric forms of the same substance, or of different substances having the same composition; as, xylene has three metamers, viz, orthoxylene, metaxylene, and paraxylene. See: Metamere. Source: Websters Dictionary (01 Mar 1998) |
| metamere | <biology> Unit of segmentation or metamerism. (18 Nov 1997) |
| metameric | 1. <chemistry> Having the same elements united in the same proportion by weight, and with the same molecular weight, but possessing a different structure and different properties; as, methyl ether and ethyl alcohol are metameric compounds. See Isomeric. The existence of metameric compounds is due to the different arrangement of the same constituents in the molecule. 2. <biology> Of or pertaining to a metamere or its formation; as, metameric segmentation. Origin: Pref. Meta- + Gr. Part. Source: Websters Dictionary (01 Mar 1998) |
| metameric nervous system | That part of the nervous system which innervates body structures developed in ontogeny from the segmentally arranged somites or, in the head region, branchial arches. The term implies reference to the neural mechanisms intrinsic to the spinal cord and brainstem (represented by the sensory nuclei, motoneuronal cell groups, and their associated interneurons in the reticular formation); by strict definition it should exclude the autonomic nervous system. (05 Mar 2000) |
| metamerism | <biology> The condition of developing body segments (such as in earthworms). (09 Oct 1997) |
| metamorphic | 1. Subject to change; changeable; variable. 2. Causing a change of structure. 3. <geology> Pertaining to, produced by, or exhibiting, certain changes which minerals or rocks may have undergone since their original deposition; especially applied to the recrystallization which sedimentary rocks have undergone through the influence of heat and pressure, after which they are called metamorphic rocks. See: Metamorphosis. Source: Websters Dictionary (01 Mar 1998) |
| metamorphism | <geology> The state or quality of being metamorphic; the process by which the material of rock masses has been more or less recrystallized by heat, pressure, etc, as in the change of sedimentary limestone to marble. Source: Websters Dictionary (01 Mar 1998) |