Template:Infobox protactinium

Protactinium,  ₉₁Pa

General properties
Name, symbol	protactinium, Pa
Appearance	bright, silvery metallic luster
Pronunciation	/ˌproʊtækˈtɪniəm/ PROH-tak-TIN-ee-əm
Protactinium in the periodic table
Pr ↑ Pa ↓ (Uqt) thorium ← protactinium → uranium
Atomic number (Z)	91
Group, block	group n/a, f-block
Period	period 7
Element category	actinide
Standard atomic weight (±) (Ar)	231.03588(2)
Electron configuration	[Rn] 5f2 6d1 7s2
per shell	2, 8, 18, 32, 20, 9, 2
Physical properties
Phase	solid
Melting point	1841 K ​(1568 °C, ​2854 °F)
Boiling point	4300 K ​(4027 °C, ​7280 °F) (?)
Density near r.t.	15.37 g/cm3
Heat of fusion	12.34 kJ/mol
Heat of vaporization	481 kJ/mol
Atomic properties
Oxidation states	2, 3, 4, 5 ​(a weakly basic oxide)
Electronegativity	Pauling scale: 1.5
Ionization energies	1st: 568 kJ/mol
Atomic radius	empirical: 163 pm
Covalent radius	200 pm
Miscellanea
Crystal structure	​tetragonal
Thermal expansion	~9.9 µm/(m·K) (at r.t.)
Thermal conductivity	47 W/(m·K)
Electrical resistivity	177 nΩ·m (at 0 °C)
Magnetic ordering	paramagnetic
CAS Number	7440-13-3
History
Prediction	Dmitri Mendeleev (1869)
Discovery and first isolation	William Crookes (1900)
Named by	Otto Hahn and Lise Meitner (1917–8)
Most stable isotopes of protactinium
iso NA half-life DM DE (MeV) DP 229Pa syn 1.5 d ε 0.311 229Th 230Pa syn 17.4 d ε 1.310 230Th 231Pa 100% 3.276×104 y α 5.150 227Ac 232Pa syn 1.31 d β− 1.337 232U 233Pa trace 26.967 d β− 0.5701 233U 234Pa trace 6.75 h β− 2.195 234U 234mPa trace 1.17 min β− 2.29 234U

References

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