Electronic data		Thermal data		Steric data
Shells: 2,8,18,32,22,9,2 Orbitals: [Rn] 5f4 6d1 7s2 Electronegativity: 1.2, -- 1. Ionization potential: 6.2657 eV 2. Ionization potential: -- eV 3. Ionization potential: -- eV Oxidation states: 6,5,4,3 Electrical conductivity: 0.00822 10^6		Melting point: 640 °C Boiling point: 3902 °C Specific heat: 0.12 J/gK Heat of fusion: 5.190 kJ/mol Heat of vaporization: -- kJ/mol Thermal conductivity: 0.063 W/cmK		Atomic radius: -- Å Ionic radius: -- Å () Covalent radius: -- Å Atomic volume: 11.62 cm³/mol Density (293 K): 20.45 g/cm³ Crystal structure: Orthorhombic

Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
235Np	0	235	5/2	1.085y	EC,	View
236Np	0	236	6	1.55E05y	EC,-	View
236Npm	0	236.047	1	22.5h	EC,-	View
237Np	0	237.048	5/2	2.14E06y		View
238Np	0	238	2	2.117d	-	View
239Np	0	239	5/2	2.355d	-	View
240Np	0	240	5	1.032h	-	View
240Npm	0	240	1	7.22m	-,IT	View

Legend

Name origin:	Named for the planet Neptune.
Description:	Rare, silvery radioactive metal.
Discovered by:	E.M. McMillan, P.H. Abelson
Year:	1940
Place:	United States
Sources:	Produced by bombarding uranium with slow neutrons.
Use(s):	It has no significant commercial applications.