91 Pa (Protactinium)
Appearance: Bright, Silvery metallic luster
Mass number: 231
Atomic weight: 231.03588(2) g/mol
Atomic number (Z): 91
Electrons: 91
Protons: 91
Neutrons: 140
Period: 7
Block: f
Element category: Actinide
Electrons per shell: K2, L8, M18, N32, O20, P9, Q2
Electron configuration: 1s22s22p63s23p63d104s24p64d105s25p64f145d106s26p65f26d1 7s2
Phase: solid
Melting point: 1841 K (1568 oC)
Boiling point: 4300 K (4027 oC)
Density: 15.37 g/cm3
Half Life(s): 1034×109
Lifetime(s): 1491×109
Decay mode: α decay
Neutron cross section (Barns): 500
Molar volume: 0.000015032 m3/mol
Heat of fusion: 12.34 kJ/mol
Heat of vaporization: 481 kJ/mol
Oxidation states: 2, 3, 4, 5
Ion charge: Pa5+, Pa4+
Electronegativity: Pauling scale: 1.5
Valence: 5
Ionization energies: 1st: 568 kJ/mol
Atomic radius: empirical: 163 pm
Covalent radius: 200 pm
Crystal structure: Tetragonal
Grid parameters: a=3.925 c=3.238
Attitude c/a: 0.82
Thermal expansion: ~9.9 μm/(m∙K)
Thermal conductivity: 47 W/(m∙K)
Electrical conductivity: 56×104 S/m
Electrical resistivity: 177 nΩ∙m
Magnetic ordering: Paramagnetic
Volume magnetic susceptibility: 0.0004995
Mass magnetic susceptibility: 325×10-10 m3/kg
Molar magnetic susceptibility: 7509×10-12 m3/mol
Critical Temperature: 1.4 K
CAS Number: 7440-13-3
Prediction: Dmitri Mendeleev (1869)
Discovery and first isolation: Kasimir Fajans and Oswald Helmuth Gohring (1913)
Named by: Otto Hahn and Lise Meitner (1917 – 8)
Isotopes: 229Pa 230Pa 231Pa 232Pa 233Pa 234Pa 234mPa
Uses: Protactinium is little used outside of research.
Biological role: It is toxic due to its radioactivity
Natural abundance: protactinium are found naturally in uranium ores in small amount. It is also found in spent fuel rods from nuclear reactors, from which it is extracted.
Abundance 9.9×10-13%(In Earth Crust), 2×10-23%(In Oceans)
#Protactinium
