Discovered By: Oswald Helmuth Gohring, John Arnold Cranston, Alexander Fleck(1st Baron Fleck), Otto Hahn, Lise Meitner, Kasimir Fajans, Frederick Soddy
Discovery year: 1913

The following table showing some properties of Protactinium(Pa):

Table Example
Atomic number 91
Group n/a
Period 7
Block 1
Electrons 91
Protons 91
Neutrons 140
Atomic weight (231.03588)
Oxidation states +4, +5
Ionic charge Pa^5+, Pa^4+


Table Example
Electrons per shell K2 L8 M18 N32 O20 P9 Q2
Electron configuration 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^10 4p^6 5s^2 4d^10 5p^6 6s^2 4f^14 5d^10 6p^6 7s^2 5f^2 6d^1
Covalent radius 200 pm
Boiling point 4000°C
Melting point 1572°C
Phase Solid
Fusion heat 15 kJ.mol^-1
Vaporization heat 470 kJ.mol^-1
Specific heat 99.1 J.kg^-1.K^-1
Color Silver


Table Example
Density 15370 kg.m^-3
Thermal conductivity 47 W.m^-1.K^-1
Electrical type Conductor
Magnetic type Paramagnetic
Resistivity 1.8*10^-7 Ohm.m
Superconducting point 1.4 K
Electronegativity 1.5
Valence 5
First ionization energy 568 kJ.mol^-1
Radioactive Yes


Table Example
Half life 1.034*10^12 s
Lifetime 1.491*10^12 s
Neutron cross section 200 barn
Decay mode Alpha emission (α-decay)