Comparison of Nickel and Erbium

Attribute	Erbium ×	Nickel ×
Atomic mass (u)	167.26	58.693
Standard state	Solid	Solid
Oxidation states	+3	+2 +3
Electron configuration	[Xe]6s²4f¹²	[Ar]4s²3d⁸
Atomic radius (van der waals) (pm)	235	163
Electronegativity (pauling scale)	1.24	1.91
Electron affinity (eV)	-	1.156
Ionization energy (eV)	6.108	7.64
Boiling point (K)	3141	3186
Melting point (K)	1802	1728
Density (g/cm³)	9.07	8.912
Atomic number	68	28
Group name	Lanthanide	Transition metal
Symbol	Er	Ni
Discovered (year)	1843	1751