Comparison of Zirconium and Thorium

Attribute	Thorium ×	Zirconium ×
Atomic mass (u)	232.038	91.22
Standard state	Solid	Solid
Oxidation states	+4	+4
Electron configuration	[Rn]7s²6d²	[Kr]5s²4d²
Atomic radius (van der waals) (pm)	237	186
Electronegativity (pauling scale)	1.3	1.33
Electron affinity (eV)	-	0.426
Ionization energy (eV)	6.08	6.634
Boiling point (K)	5061	4682
Melting point (K)	2023	2128
Density (g/cm³)	11.72	6.52
Atomic number	90	40
Group name	Actinide	Transition metal
Symbol	Th	Zr
Discovered (year)	1828	1789