Periodic TableNeptunium (Np)
Neptunium is an actinide with atomic number 93, in period 7, in the f-block of the periodic table. Its atomic mass is 237 u and its electron configuration is [Rn] 5f⁴ 6d¹ 7s². Solid at 25 °C.
Key facts
| Atomic number | 93 |
|---|---|
| Atomic mass | 237 u |
| Category | Actinide |
| Period | 7 |
| Group | f-block, no group number |
| Block | f |
| Electron configuration | [Rn] 5f⁴ 6d¹ 7s² |
| Electrons per shell | 2, 8, 18, 32, 22, 9, 2 |
| Electronegativity (Pauling) | 1.36 |
| Oxidation states | +2, +3, +4, +5, +6, +7common in bold |
| State at 25 °C | Solid |
| Melting point | 917 K643.85 °C |
| Boiling point | 4175 K3901.85 °C |
| Density | 20.45 g/cm³ |
Atomic properties
| First ionization energy | 6.266 eV |
|---|---|
| Electron affinity | --- |
| Atomic radius | 130 pm |
| Covalent radius | 190 pm |
| Van der Waals radius | 221 pm |
| Common ions | Np⁵⁺ |
| Protons, neutrons, electrons | 93, 144, 93 |
Physical and thermal properties
| Molar volume | 11.59 cm³/mol |
|---|---|
| Heat of fusion | 10 kJ/mol |
| Heat of vaporization | 335 kJ/mol |
| Specific heat | 124 J/(kg·K) |
| Thermal conductivity | 6 W/(m·K) |
| Thermal expansion | --- |
| Mohs hardness | --- |
| Young’s modulus | --- |
| Crystal structure | Simple orthorhombic |
| Magnetic type | Paramagnetic |
Identification and history
| CAS number | 7439-99-8 |
|---|---|
| Latin name | Neptunium |
| Discovered by | E. McMillan, P. Abelson · 1940 |
| Named by | --- |
Natural isotopes
Neptunium has no stable isotopes: every isotope is radioactive.
Data checked against PubChem (NIH), IUPAC, the NIST Atomic Spectra Database and the IAEA (NUBASE and AME), the same data you see in the app.
A dash (---) means there is no reliable published measurement. The app never makes one up.
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