protactinium

[ proh-tak-tin-ee-uh m ]
/ ˌproʊ tækˈtɪn i əm /

noun Chemistry.

a radioactive, metallic element. Symbol: Pa; atomic number: 91.
Also protoactinium.

Origin of protactinium

First recorded in 1915–20; prot- + actinium

Words nearby protactinium

prosumer, prosy, prosyllogism, prot-, prot., protactinium, protagonist, protagoras, protamine, protandrous, protanomaly

British Dictionary definitions for protactinium

protactinium
/ (ˌprəʊtækˈtɪnɪəm) /

noun

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, 231 Pa: 32 500 years; valency: 4 or 5; relative density: 15.37 (calc.); melting pt: 1572°C Former name: protoactinium

Medical definitions for protactinium

protactinium
[ prō′tăk-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.

Scientific definitions for protactinium

protactinium
[ prō′tăk-tĭn′ē-əm ]

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.