Comparison of Gadolinium and Actinium

Attribute	Actinium ×	Gadolinium ×
Standard state	Solid	Solid
Electron configuration	[Rn]7s²6d¹	[Xe]6s²4f⁷5d¹
Atomic mass (u)	227.02775	157.2
Electronegativity (pauling scale)	1.1	1.2
Oxidation states	+3	+3
Ionization energy (eV)	5.17	6.15
Atomic radius (van der waals) (pm)	260	237
Boiling point (K)	3471	3546
Melting point (K)	1324	1586
Density (g/cm³)	10.07	7.9
Atomic number	89	64
Group name	Actinide	Lanthanide
Discovered (year)	1899	1880
Symbol	Ac	Gd