Comparison of Neodymium and Promethium

Attribute	Promethium ×	Neodymium ×
Standard state	Solid	Solid
Electron configuration	[Xe]6s²4f⁵	[Xe]6s²4f⁴
Atomic mass (u)	144.91276	144.24
Electronegativity (pauling scale)	-	1.14
Oxidation states	+3	+3
Ionization energy (eV)	5.55	5.525
Atomic radius (van der waals) (pm)	236	229
Boiling point (K)	3273	3347
Melting point (K)	1315	1294
Density (g/cm³)	7.26	7.01
Atomic number	61	60
Group name	Lanthanide	Lanthanide
Symbol	Pm	Nd
Discovered (year)	1945	1885