protactinium

pro·tac·tin·i·um  (prtk-tn-m)

n. Symbol Pa

A rare, extremely toxic, radioactive element chemically similar to uranium, having 13 known isotopes, the most common of which is protactinium 231 with a half-life of 32,480 years. Atomic number 91; melting point 1,230°C; specific gravity 15.37; valence 4, 5. See Table at element.

---

[prot(o)- + actinium (so called because it decays into actinium).]

---

protactinium

Noun

Chem a toxic radioactive metallic element Symbol: Pa

---

protactinium  (prtk-tn-m)

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.

Thesaurus

Noun

1.

protactinium - a short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead atomic number 91, protoactinium, Pa metal, metallic element - any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.