Difference between Atomic Number 91 and Protactinium

ATOMIC NUMBER 91 vs PROTACTINIUM: NOUN

A short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead

A chemical element (symbol Pa) with atomic number 91.
A rare, extremely toxic, radioactive, lustrous, metallic element having more than 30 known isotopes and isomers, the most common of which is Pa-231 with a half-life of 32,760 years. Atomic number 91; atomic weight 231.036; melting point 1,572°C; specific gravity 15.37 (calculated); valence 2, 3, 4, 5. : Periodic Table.
A short-lived radioactive metallic element formed from uranium and disintegrating into actinium and then into lead

The radioactive chemical element, of atomic number 91; Atomic symbol Pa; at. wt. of longest-lived isotope, 231 (T1/2 = 32,500 yrs.) Also called brevium, Uranium X2 and UX2.

Argon, Nitrogen, Magnesium, Iodine, Curium, Radon, Erbium, Transuranic, Gallium, Zirconium, Praseodymium, Bromine, Lanthanum, Protoactinium, Protactinium

Hafnium, Fluorine, Boron, Argon, Nitrogen, Magnesium, Iodine, Radon, Erbium, Transuranic, Gallium, Zirconium, Praseodymium, Bromine, Lanthanum

Protactinium is both toxic and highly radioactive and thus all manipulations with it are performed in a sealed glove box.
For thorium, protactinium and uranium the highest accessible oxidation state is the most stable one as well in aqueous solution.
The monoxide PaO has only been observed as a thin coating on protactinium metal, but not in an isolated bulk form.
For these reasons, development of a more efficient method of protactinium removal is needed.
The symbol Pa stands for the element protactinium.
Protactinium has a bright metallic luster which it retains for some time in air.
Protactinium(V) fluoride and protactinium(V) chloride have a polymeric structure of monoclinic symmetry.