Comparison of Phosphorus and Selenium

Attribute	Selenium ×	Phosphorus ×
Atomic mass (u)	78.97	30.973762
Standard state	Solid	Solid
Oxidation states	-2 +4 +6	-3 +3 +5
Electron configuration	[Ar]4s²3d¹⁰4p⁴	[Ne]3s²3p³
Atomic radius (van der waals) (pm)	190	180
Electronegativity (pauling scale)	2.55	2.19
Electron affinity (eV)	2.021	0.746
Ionization energy (eV)	9.752	10.487
Boiling point (K)	958	553.65
Melting point (K)	493.65	317.3
Density (g/cm³)	4.809	1.82
Atomic number	34	15
Group name	Nonmetal	Nonmetal
Discovered (year)	1817	1669
Symbol	Se	P