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Protactinium at Chemical Elements.com
Basic Information | Atomic Structure | Isotopes | Related Links | Citing This Page

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

Atomic Structure

[Bohr Model of Protactinium]  
Number of Energy Levels: 7

    First Energy Level: 2
    Second Energy Level: 8
    Third Energy Level: 18
    Fourth Energy Level: 32
    Fifth Energy Level: 20
    Sixth Energy Level: 9
    Seventh Energy Level: 2


Isotope Half Life
Pa-23017.4 days
Pa-23132800.0 years
Pa-23327.0 days
Pa-2346.69 hours
Pa-234m1.17 minutes


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

Related Links

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Bentor, Yinon. Chemical Element.com - Protactinium. <http://www.chemicalelements.com/elements/pa.html>.

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