Symbol: Pa
Atomic Number: 91
Atomic Weight: 231.03588
Element Classification: Radioactive Rare Earth Element (Actinide Series)
Discovered By: Fredrich Soddy, John Cranston, Otto Hahn, Lise Meitner
Discovery Date: 1917 (England/France)
Name Origin: Greek: proto and actinium (parent of actinium); it forms actinium when it radioactively decays.
Density (g/cc): 15.37
Melting Point (K): 2113
Boiling Point (K): 4300
Appearance: Silvery-white, radioactive metal
Atomic Radius (pm): 161
Atomic Volume (cc/mol): 15.0
Covalent Radius (pm): n/a
Ionic Radius: 89 (+5e) 113 (+3e)
Specific Heat (@20°C J/g mol): 0.121
Fusion Heat (kJ/mol): 16.7
Evaporation Heat (kJ/mol): 481.2
Thermal Conductivity (@25°C W/m K):
Debye Temperature (K): n/a
Pauling Negativity Number: 1.5
First Ionizing Energy (kJ/mol): n/a
Oxidation States: 5, 4
Electronic Configuration: [Rn] 5f² 6d¹ 7s²
Lattice Structure: Tetragonal (TET)
Lattice Constant (Å): 3.920
Lattice C/A Ratio: n/a