Comparison of Gadolinium and Terbium

Attribute	Gadolinium ×	Terbium ×
Standard state	Solid	Solid
Electron configuration	[Xe]6s²4f⁷5d¹	[Xe]6s²4f⁹
Atomic mass (u)	157.2	158.92535
Electronegativity (pauling scale)	1.2	-
Oxidation states	+3	+3
Ionization energy (eV)	6.15	5.864
Atomic radius (van der waals) (pm)	237	221
Boiling point (K)	3546	3503
Melting point (K)	1586	1629
Density (g/cm³)	7.9	8.23
Atomic number	64	65
Group name	Lanthanide	Lanthanide
Symbol	Gd	Tb
Discovered (year)	1880	1843