Comparison of Selenium and Cesium

Attribute	Selenium ×	Cesium ×
Atomic mass (u)	78.97	132.905452
Standard state	Solid	Solid
Oxidation states	-2 +4 +6	+1
Electron configuration	[Ar]4s²3d¹⁰4p⁴	[Xe]6s¹
Atomic radius (van der waals) (pm)	190	343
Electronegativity (pauling scale)	2.55	0.79
Electron affinity (eV)	2.021	0.472
Ionization energy (eV)	9.752	3.894
Boiling point (K)	958	944
Melting point (K)	493.65	301.59
Density (g/cm³)	4.809	1.93
Atomic number	34	55
Group name	Nonmetal	Alkali metal
Discovered (year)	1817	1860
Symbol	Se	Cs