Neptunium
The first synthetic transuranium element, beyond uranium.
Inside the Neptunium atom
Switch between Bohr and Quantum Cloud modes to compare a simple teaching model with a more realistic probability-based view, and follow the guided tour to explore the Neptunium atom step by step.
Electron configuration
[Rn] 5f4 6d1 7s2
A neutral Neptunium atom has 93 electrons (equal to its proton count). Choosing a different isotope above changes only the neutron count.
Shell distribution
Electrons fill inner shells before outer ones; the outermost (valence) shell drives the element's chemistry.
Physical & atomic properties
- State (room temp)
- Solid
- Melting point
- 917 K (644 °C)
- Boiling point
- 4273 K (4000 °C)
- Density
- 20.45 g/cm³
- Electronegativity
- 1.36 Pauling
- Atomic radius
- 175 pm
- 1st ionization energy
- 605 kJ/mol
- Category
- Actinides
Discovery & naming
- Discovered
- 1940
- Discovered by
- Edwin McMillan and Philip Abelson
- Origin of name
- The planet Neptune.
Notable uses
Neutron-detection instruments and research.
Where Neptunium comes from
Human synthesis
The first transuranium element. Trace amounts occur in uranium ores; useful quantities come from reactors.
Simplified origin map — many elements form through more than one astrophysical pathway.
Summary
- Atomic number
- 93
- Atomic mass
- [237]
- Category
- Actinides
- Group · Period
- — · 7
- Block
- f-block
- Shells
- 2 · 8 · 18 · 32 · 22 · 9 · 2