Protactinium Pa (Element 91) of Periodic Table

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)


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