Elementymology & Elements Multidict

memory peg	Shiny radioactive metal melting point <=1600 °C; <=2912 °F boiling point -- °C; -- °F density 15.37 g/cc; 959.52 pounds/cubic foot
1913 Kasimir Fajans & Otto Göhring
πρωτος (prōtos) + Actinium = first (Greek) + element #89 named by Otto Hahn and Lise Meitner, 1918

Element #91 was predicted by Д.И. Менделеев (D.I. Mendeleyev) in 1871 and named by him Eka-Tantalum (note) .

The first isotope of Protactinium to be discovered was ²³⁴Pa^m (also called Uranium X₂), an ephemeral member of the natural decay series of ²³⁸U. This isotope was identified by Kasimir Fajans (1887-1975) and Otto H. Göhring of Karlsruhe in 1913, who called it Brevium (= brief), because of its short half-life (note).

In 1918, two research scientist teams isolated almost simultaneously a more stable isotope (²³¹Pa), of the decay series of ²³⁵U. These teams were led by Otto Hahn and Lise Meitner (note), and by Frederick Soddy and John A. Cranston (note). The first team named this isotope Protoactinium, from the Greek πρωτος [prōtos] = first, since its place in the uranium-actinium decay series it is the first before Actinium (it falls apart in Actinium (²²⁷Ac) and an α-particle).
The isotope name Protoactinium was shortened in 1949 to Protactinium and became the general name for the element #91.

Historical names of Protactinium Isotopes

Name & Symbol (hist. and modern)			First described		Notes
Protoactinium	Pa	231Pa	1918	O. Hahn & L. Meitner
Uranium Z	U Z	234Pa	1918	O. Hahn
Uranium X2 Brevium	U X2 Bv	234Pam	1913	K. Fajans & O. Göhring

John and Gordon Marks suggested in 1994 the name Meitnium (Mt), after Lise Meitner, according to them the discoverer of this element and of the many peculiar properties (especially radioactivity) of the actinides. The Marks brothers found the old names ugly and confusing. They offered alternative names that are equivalent contemporary (at the time and place of discovery) metaphors, both more euphonious and more memorable (note).

• Mary Elvira Weeks, Discovery of the Elements, comp. rev. by Henry M. Leicester (Easton, Pa.: Journal of Chemical Education, 1968), pp. 783-784, 791-795.
• Protactinium und Isotope. Gmelins Handbuch der anorganische Chemie, 8. Aufl.; System-Nummer 41 (1952).