Comparison of Beryllium and Erbium

Attribute	Erbium ×	Beryllium ×
Standard state	Solid	Solid
Electron configuration	[Xe]6s²4f¹²	[He]2s²
Atomic mass (u)	167.26	9.012183
Electronegativity (pauling scale)	1.24	1.57
Oxidation states	+3	+2
Ionization energy (eV)	6.108	9.323
Atomic radius (van der waals) (pm)	235	153
Boiling point (K)	3141	2744
Melting point (K)	1802	1560
Density (g/cm³)	9.07	1.85
Atomic number	68	4
Group name	Lanthanide	Alkaline earth metal
Discovered (year)	1843	1798
Symbol	Er	Be