Basic Information

Name: Protactinium 
Symbol: Pa 
Atomic Number: 91 
Atomic Mass: 231.03587 amu 
Melting Point: 1600.0 °C (1873.15 K, 2912.0 °F) 
Boiling Point: Unknown 
Number of Protons/Electrons: 91 
Number of Neutrons: 140 
Classification: Rare Earth 
Crystal Structure: Orthorhombic 
Density @ 293 K: 15.4 g/cm3 
Color: Unknown
Date of Discovery: 1917 
Discoverer: Fredrich Soddy 
Name Origin: From the Greek word protos (first) 
Uses: No uses known 
Obtained From: fission product of uranium, thorium, plutonium