Comparison of Hydrogen and Helium

Attribute	Helium ×	Hydrogen ×
Atomic mass (u)	4.0026	1.008
Standard state	Gas	Gas
Oxidation states	0	-1 +1
Electron configuration	1s²	1s¹
Atomic radius (van der waals) (pm)	140	120
Electronegativity (pauling scale)	-	2.2
Electron affinity (eV)	-	0.754
Ionization energy (eV)	24.587	13.598
Boiling point (K)	4.22	20.28
Melting point (K)	0.95	13.81
Density (g/cm³)	0.0001785	8.988E-5
Atomic number	2	1
Group name	Noble gas	Nonmetal
Symbol	He	H
Discovered (year)	1868	1766