Comparison of Sodium and Rubidium

Attribute	Sodium ×	Rubidium ×
Atomic mass (u)	22.9897693	85.468
Standard state	Solid	Solid
Oxidation states	+1	+1
Electron configuration	[Ne]3s¹	[Kr]5s¹
Atomic radius (van der waals) (pm)	227	303
Electronegativity (pauling scale)	0.93	0.82
Electron affinity (eV)	0.548	0.468
Ionization energy (eV)	5.139	4.177
Boiling point (K)	1156	961
Melting point (K)	370.95	312.46
Density (g/cm³)	0.97	1.53
Atomic number	11	37
Group name	Alkali metal	Alkali metal
Discovered (year)	1807	1861
Symbol	Na	Rb