| 单词 |
covalence |
| 释义 |
covalence Chem.|kəʊˈveɪləns|
[f. co- 3 a + valence2 3.]
= covalency a, b.
1919I. Langmuir in Proc. Nat. Acad. Sci. V. 255 It is therefore proposed to define valence as the number of pairs of electrons which a given atom shares with others. In view of the fact..that valence is very often used to express something quite different, it is recommended that the word covalence be used to denote valence defined as above. Ibid. 256 In sodium chloride the covalence of both sodium and chlorine is zero. 1948Glasstone Physical Chem. (ed. 2) i. 104 The covalence of any element, not including dative covalences, should consequently be equal to the number of electrons with unpaired spins in the given atom. 1957Encycl. Brit. XXII. 946/1 Another kind of valence of great importance is ‘covalence’, which results from the sharing of two electrons by two atoms.
Hence coˈvalent a., coˈvalently adv.
1927Covalent [see electro-valent adj. s.v. electro-]. 1946Nature 12 Oct. 519/1 In compounds containing hexavalent chromium..the bond between chromium and oxygen is not fully ionic but partially covalent in nature. 1962P. J. & B. Durrant Introd. Adv. Inorg. Chem. iv. 112 The nitrogen molecule may be considered as two nitrogen atoms linked by a triple covalent bond... In the molecule there are ten valency electrons, six of which are shared. 1962S. G. Waley in A. Pirie Lens Metabolism Rel. Cataract 357 Both biotin and lipoic acid..are covalently bound to protein. |
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