Comparison of Rubidium and Cesium

Attribute	Rubidium ×	Cesium ×
Atomic mass (u)	85.468	132.905452
Standard state	Solid	Solid
Oxidation states	+1	+1
Electron configuration	[Kr]5s¹	[Xe]6s¹
Atomic radius (van der waals) (pm)	303	343
Electronegativity (pauling scale)	0.82	0.79
Electron affinity (eV)	0.468	0.472
Ionization energy (eV)	4.177	3.894
Boiling point (K)	961	944
Melting point (K)	312.46	301.59
Density (g/cm³)	1.53	1.93
Atomic number	37	55
Group name	Alkali metal	Alkali metal
Discovered (year)	1861	1860
Symbol	Rb	Cs