Comparison of Cobalt and Erbium

Attribute	Erbium ×	Cobalt ×
Atomic mass (u)	167.26	58.93319
Standard state	Solid	Solid
Oxidation states	+3	+2 +3
Electron configuration	[Xe]6s²4f¹²	[Ar]4s²3d⁷
Atomic radius (van der waals) (pm)	235	192
Electronegativity (pauling scale)	1.24	1.88
Electron affinity (eV)	-	0.661
Ionization energy (eV)	6.108	7.881
Boiling point (K)	3141	3200
Melting point (K)	1802	1768
Density (g/cm³)	9.07	8.86
Atomic number	68	27
Group name	Lanthanide	Transition metal
Symbol	Er	Co
Discovered (year)	1843	1735