Protoactinium, Pa, is a metallic element, found in the actinide
series of inner transition metals in
Group IIIa of the periodic table.
- Atomic Number : 91
- Relative Atomic Mass : 231.04
Protoactinium was discovered by Soddy in 1917AD, and
independently by Hahn and Meitner at about the same time.
Protoactinium was isolated as the metal by von Grosse in 1935AD.
Protoactinium occurs in pitchblende.
- is fissionable with low energy neutrons and
- forms a reverse pair with Thorium, Th, in the Periodic Table
(i.e. the atomic weight of protoactinium is less than that of thorium).
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