Neptunium

Chaitra 26/06/2026 19:58:09 Updated 26/06/2026 19:58:09

Property	Value
Atomic Number	93
Element	Neptunium
Symbol	Np
Atomic Mass	[237] (most stable isotope)
Number of Neutrons	144 (Neptunium-237)
Number of Protons	93
Number of Electrons	93
Period	7
Group	Actinide (no fixed group number)
Phase	Solid
Radioactive	Yes
Natural	No (trace amounts occur in uranium ores)
Metal	Yes
Nonmetal	No
Metalloid	No
Type	Actinide
Atomic Radius	~260 pm (estimated)
Electronegativity	1.36 (estimated)
First Ionization Energy	6.266 eV (estimated)
Density	20.45 g/cm³
Melting Point	644 °C
Boiling Point	3902 °C (estimated)
Number of Isotopes	No stable isotopes (Np-237 most notable)
Discoverer	Edwin McMillan, Philip H. Abelson
Year	1940
Specific Heat	— (not well established)
Number of Shells	7
Number of Valence Electrons	5