Comparison of Niobium and Hafnium

Attribute	Hafnium ×	Niobium ×
Atomic mass (u)	178.49	92.90637
Standard state	Solid	Solid
Oxidation states	+4	+3 +5
Electron configuration	[Xe]6s²4f¹⁴5d²	[Kr]5s¹4d⁴
Atomic radius (van der waals) (pm)	212	207
Electronegativity (pauling scale)	1.3	1.6
Electron affinity (eV)	-	0.893
Ionization energy (eV)	6.825	6.759
Boiling point (K)	4876	5017
Melting point (K)	2506	2750
Density (g/cm³)	13.3	8.57
Atomic number	72	41
Group name	Transition metal	Transition metal
Symbol	Hf	Nb
Discovered (year)	1923	1801