protactinium

American  

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

noun

Chemistry.

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

---

protactinium British  

/ 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 Scientific  

/ prō′tăk-tĭn′ē-əm /

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

---

Etymology

Origin of protactinium

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.

From Scientific American

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

From Salon

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

From New York Times

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

From Nature

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

From Scientific American