Protactinium
[proh-tak-tin-ee-uh m] /ˌproʊ tækˈtɪn i əm/
noun, Chemistry.
1.
a radioactive, metallic element. Symbol: Pa; atomic number: 91.
protactinium
/ˌprəʊtækˈtɪnɪəm/
noun
1.
a toxic radioactive metallic element that occurs in uranium ores and is produced by neutron irradiation of thorium. Symbol: Pa; atomic no: 91; half-life of the most stable isotope, 231Pa: 32 500 years; valency: 4 or 5; relative density: 15.37 (calc.); melting pt: 1572°C Former name protoactinium
protactinium pro·tac·tin·i·um (prō’tāk-tĭn’ē-əm)
n.
Symbol Pa
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; melting point 1,572°C; specific gravity 15.37; valence 4, 5.
protactinium
(prō’tāk-tĭn’ē-əm)
Symbol Pa
A rare, extremely toxic, radioactive metallic element of the actinide series that occurs in uranium ores. It has 13 known isotopes, the most stable of which is protactinium 231 with a half-life of 32,760 years. Atomic number 91; approximate melting point 1,550°C; specific gravity 15.37; valence 4, 5. See Periodic Table.
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