protactinium

[proh-tak-tin-ee-uhm]

noun

Chemistry.

1. a radioactive, metallic element. Pa; 91.

protactinium

/ ˌprəʊtækˈtɪnɪəm /

noun

1. Former name: protoactinium. 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

protactinium

1. 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.

2. See Periodic Table

Word History and Origins

Origin of protactinium¹

First recorded in 1915–20; prot- + actinium

Example Sentences

In 1924, they earned their first joint Nobel Prize nomination for their work with the new element protactinium.

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In this process, they produce specific isotopes of other radioactive elements such as thorium, protactinium and radium.

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Over time, that elemental uranium has partly decayed into thorium and protactinium.

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Hahn and Meitner discovered protactinium while they were looking for the ‘mother substance’ of actinium in the radioactive decay series.

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Around that same time, Meitner and Hahn discovered the isotope protactinium, which won Meitner the Leibniz Medal.

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