protactinium


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protactinium

 (Pa) [pro″tak-tin´e-um]
a chemical element, atomic number 91, atomic weight 231. (See Appendix 6.)

pro·tac·tin·i·um (Pa),

(prō'tak-tin'ē-ŭm),
A radioactive element, atomic no. 91, atomic wt. 231.03588, formed in the decay of uranium and thorium; its most long-lived isotope, 231Pa, has a half-life of 32,500 years.
[G. prōtos, first]

pro·tac·tin·i·um

(Pa) (prō'tak-tin'ē-ŭm)
A radioactive element, atomic no. 91, atomic wt. 231.03588, formed in the decay of uranium and thorium; its longest-lived isotope, 231Pa, has a half-life of 32,500 years.
[G. prōtos, first]
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References in periodicals archive ?
Under Marchal's direction, she is using mathematical models to understand how two heavy elements, protactinium and thorium, can reveal how the Atlantic Ocean circulated in the past.
The six following elements (No.'s 84 to 89) are radioactive and exist in Nature in insignificant quantities, and are followed by the significant radioactive elements thorium, protactinium and uranium (Z = 90, 91, and 92 respectively).
Hahn and Meitner, who had discovered protactinium (see 1917), were investigating the matter.