actinium Chem.
(ækˈtɪnɪəm)
[mod.L. in form, f. Gr. ἀκτῖν- ray + -ium, as in sodium, potassium, etc.]
1. A supposed chemical element, a metal discovered in 1881 in association with zinc; so called because of the action of light upon its salts.
| 1881 Nature XXIV. 428 The existence of a new metallic element, actinium, in the zinc of commerce. Ibid. No. 620, 470 On the New Metal Actinium, by J. L. Phipson. The sulphide of actinium is described as a pale yellow canary-coloured substance. |
2. A radioactive metallic element found, associated with thorium, in pitchblende. Symbol Ac; atomic weight 227; atomic number 89.
| [1900 A. Debierne in Compt. Rend. CXXX. 906.] 1900 Jrnl. Chem. Soc. LXXVIII. ii. 350 (title) Actinium: A New Radio-active Element. Ibid. 351 The rays emitted by actinium produce the same effects as those from radium and polonium. 1906 Rutherford in Phil. Mag. XII. 362 In order to obtain a homogeneous source of α rays, the active deposit of actinium was used... This active deposit consists of two products, actinium A and B, the former of which is rayless. 1958 R. D. Connor in O. R. Frisch Nucl. Handbk. iv. §4 It gradually became clear that there existed three naturally-occurring families of radio⁓active substances, called the Uranium-Radium Series, the Thorium Series and the Actinium Series. Ibid. iv. §24 Actinium..can be produced artificially by bombarding radium (Ra226) with neutrons. |