Comparison of Protactinium and Californium

Attribute	Californium ×	Protactinium ×
Atomic mass (u)	251.07959	231.03588
Standard state	Solid	Solid
Oxidation states	+3	+4 +5
Electron configuration	[Rn]7s²5f¹⁰	[Rn]7s²5f²6d¹
Atomic radius (van der waals) (pm)	245	243
Electronegativity (pauling scale)	1.3	1.5
Melting point (K)	1173	1845
Ionization energy (eV)	6.3	5.89
Density (g/cm³)	-	15.37
Atomic number	98	91
Group name	Actinide	Actinide
Symbol	Cf	Pa
Discovered (year)	1950	1913