Comparison of Niobium and Rhenium

Attribute	Rhenium ×	Niobium ×
Atomic mass (u)	186.207	92.90637
Standard state	Solid	Solid
Oxidation states	+4 +6 +7	+3 +5
Electron configuration	[Xe]6s²4f¹⁴5d⁵	[Kr]5s¹4d⁴
Atomic radius (van der waals) (pm)	217	207
Electronegativity (pauling scale)	1.9	1.6
Electron affinity (eV)	0.15	0.893
Ionization energy (eV)	7.88	6.759
Boiling point (K)	5869	5017
Melting point (K)	3459	2750
Density (g/cm³)	20.8	8.57
Atomic number	75	41
Group name	Transition metal	Transition metal
Discovered (year)	1925	1801
Symbol	Re	Nb