Comparison of Lanthanum and Neptunium

Attribute	Neptunium ×	Lanthanum ×
Atomic mass (u)	237.048172	138.9055
Standard state	Solid	Solid
Oxidation states	+3 +4 +5 +6	+3
Electron configuration	[Rn]7s²5f⁴6d¹	[Xe]6s²5d¹
Atomic radius (van der waals) (pm)	221	240
Electronegativity (pauling scale)	1.36	1.1
Electron affinity (eV)	-	0.5
Ionization energy (eV)	6.266	5.577
Boiling point (K)	4175	3737
Melting point (K)	917	1191
Density (g/cm³)	20.25	6.15
Atomic number	93	57
Group name	Actinide	Lanthanide
Symbol	Np	La
Discovered (year)	1940	1839