Neptunium
Main page |
| Other names/abbreviations: | Np |
| Element no: | 93 |
| Element group: | Actinides |
| Element type: | Inner transition metals |
| CAS-Number: | 7439-99-8 |
| EINECS-Number: | 231-108-8 |
Physical properties
Appearance | ||
| Physical state @ 20°C: | Solid | |
| Color: | Silvery [3] | |
Bulk properties | ||
| Molecular weight (g/mol): | 237.0482 [1] | |
| Melting point (°C): | 644 [1] | |
| Boiling point (°C): | 3902 (Approximately) [1] | |
| Density (g/cm3): | alpha-Np: 20.25 [3] beta-Np: 19.36 (313 °C) [3] gamma-Np: 18.0 (600 °C) [3] | |
| Elastic properties: Youngs modulus (GPa): Bulk modulus (GPa): |
80 [2] 118 [2] | |
Thermodynamic properties | ||
| ΔH°fusion (kJ/mol): | 3.20 [3] | |
| ΔH°vaporization (kJ/mol): | 336 [1] | |
Crystal structure | ||
| Crystal type: | alpha-Np: Orthorhombic [2,3] beta-Np (>280 °C): Tetragonal [3] gamma-Np (>577 °C): Cubic [3] | |
Electronic properties | ||
 |
Electron configuration: | 1s2-2s2-2p6-3s2-3p6-4s2-3d10-4p6-4d10-4f14-5s2-5p6-5d10-5f4-6s2-6p6-6d1-7s2 | Ionic radius (Å): | Np(VII): 0.71 (6-coordinate) [1] Np(VI): 0.72 (6-coordinate) [1] Np(V): 0.75 (6-coordinate) [1] Np(IV): 0.87 (6-coordinate) [1] Np(III): 1.01 (6-coordinate) [1] Np(II): 1.10 (6-coordinate) [1] |
Conductivity | ||
| e°(V): | NpO22+/NpO2+: 1.24 [1] NpO2+/Np(IV): 0.64 [1] Np(IV)/Np(III): 0.15 [1] Np(IV)/Np: -1.30 [1] Np(III)/Np: -1.79 [1] | |
| Electrical resisitvity (μΩ·cm): | 122 (22 °C) [1] 116.4 (37 °C) [2] | |
| Thermal (W/m·K): | 6.3 (27 °C) [3] | |
History
Discovery239Np was discovered by E.M. McMillan and P.H. Abelson in 1940 at Berkeley, California, USA, who bombarded uranium with neutrons produced from a cyclotron. It was the first synthetic transuranium (elements after uranium) element discovered [3].
Origin of name
Named after the planet Neptune, as it is the next planet after Uranus, that gave name to uranium [1]
References
1: Greenwood,N.N., Earnshaw,A. Chemistry of the elements2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain
2: Buch,A. Pure Metals Properties. A Scientific-Technical Handbook
1st edition (1999) Edited by Buch,A. pp. 1-306, ASM International and Freund Publishing House Ltd. Ohio. USA
3: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA
© Michael Pilgaard
Created: October 4, 2008