Comparison of Protactinium and Fermium

Attribute	Protactinium ×	Fermium ×
Atomic mass (u)	231.03588	257.09511
^1↑Standard state	Solid	Solid
Oxidation states	+4 +5	+3
Electron configuration	[Rn]7s²5f²6d¹	[Rn]5f¹²7s²
Atomic radius (van der waals) (pm)	243	-
Electronegativity (pauling scale)	1.5	1.3
Melting point (K)	1845	1800
Ionization energy (eV)	5.89	6.5
Density (g/cm³)	15.37	-
Atomic number	91	100
Group name	Actinide	Actinide
Symbol	Pa	Fm
Discovered (year)	1913	1952