protactinium /pro·tac·tin·i·um/ (Pa) (pro″tak-tin´e-um) chemical element, at. no. 91.
protactinium (Pa)
protactinium (Pa) [pro″tak-tin´e-um]
pro·tac·tin·i·um (pr  t k-t n  - m)n. Symbol Pa1 A rare, extremely toxic radioactive element having 13 known isotopes, the most stable of which is Pa 231 with a half-life of 32,700 years. Atomic number 91. |
protactinium (Pa)
[-taktin′ē·əm]
Etymology: Gk, protos, first, aktis, ray
a radioactive element. Its atomic number is 91, and its atomic mass is 231.04. Its decay products are actinium and an alpha particle. See also actinium.
protactinium (Pa) [pro″tak-tin´e-um]
a chemical element, atomic number 91, atomic weight 231. (See Appendix 6.)
protactinium
a chemical element, atomic number 91, atomic weight 231, symbol Pa. See Table 6.
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