General | States | Energies | Oxidation & Electrons |Appearance & Characteristics
Reactions | Other Forms |Radius | Conductivity | Abundance
Encyclopedia Britannica articles


Name Neptunium Symbol Np
atomic number 93 Atomic weight 237.0482
Density @ 293 K 20.45 g/cm3 Atomic volume 11.62 cm3/mol
Group Rare Earth, Actinides discovered 1940


state (s, l, g) s
melting point 913.2 K boiling point 4175 K
Heat of fusion 5.190 kJ/mol Heat of vaporization ?
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1st ionization energy 597 kJ/mole electronegativity 1.3
2nd ionization energy kJ/mole electron affinity kJ/mole
3rd ionization energy kJ/mole Specific heat 0.12 J/gK
heat atomization kJ/mole atoms

Oxidation & Electrons

Shells 2,8,18,32,23,8,2 electron configuration [Rn] 5f4 6d1 7s2
minimum oxidation number 0 maximum oxidation number 7
min. common oxidation no. 0 max. common oxidation no. 5
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Appearance & Characteristics

structure special:complex color silvery
uses toxicity
hardness mohs characteristics Radioactive


reaction with air reaction with 6M HCl
reaction with 6M HCl reaction with 15M HNO3
reaction with 6M NaOH
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Other Forms

number of isotopes 0 hydride(s) NpH2 NpH3
oxide(s) NpO NpO2 Np2O5 chloride(s) NpCl3 NpCl4


ionic radius (2- ion) pm ionic radius (1- ion) pm
atomic radius 155 pm ionic radius (1+ ion) pm
ionic radius (2+ ion) 124 pm ionic radius (3+ ion) 115 pm
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thermal conductivity 6.3 J/m-sec-deg electrical conductivity 1/mohm-cm
polarizability 24.8 A^3


source Synthetic rel. abund. solar system log
abundance earth's crust log cost, pure $/100g
cost, bulk $/100g
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World Wide Web presentation of Chemicool Periodic Table is © Copyright 1996-99 by David D. Hsu. Some data were provided by and used with the permission of JCE Software and is owned and copyright by the Division of Chemical Education, Inc. Additional data were provided by Perkin-Elmer through Peter Lykos of IIT. The information may not be redistributed without the permission of David Hsu or JCE Software.