Comparison of Chromium and Erbium

Attribute	Erbium ×	Chromium ×
Atomic mass (u)	167.26	51.996
Standard state	Solid	Solid
Oxidation states	+3	+2 +3 +6
Electron configuration	[Xe]6s²4f¹²	[Ar]3d⁵4s¹
Atomic radius (van der waals) (pm)	235	189
Electronegativity (pauling scale)	1.24	1.66
Electron affinity (eV)	-	0.666
Ionization energy (eV)	6.108	6.767
Boiling point (K)	3141	2944
Melting point (K)	1802	2180
Density (g/cm³)	9.07	7.15
Atomic number	68	24
Group name	Lanthanide	Transition metal
Symbol	Er	Cr
Discovered (year)	1843	1797