Neptunium: the essentials

Neptunium is a radioactive rare earth metal and has at least 3 allotropic forms. It is named for the planet Neptune. Np-237 is a by-product from nuclear reactors.

Neptunium: historical information

Neptunium was the first synthetic transuranium element of the actinide series. It was discovered by McMillan and 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.

Neptunium around us Read more »

Neptunium has no biological role.

Trace amounts of neptunium are present in uranium ores. In practice, isolable amounts are best extracted from spent uranium fuel rods produced in nuclear reactors.

Abundances for neptunium in a number of different environments. More abundance data »

Location	ppb by weight	ppb by atoms	Links
Universe	(no data)	(no data)
Crustal rocks	(no data)	(no data)
Human	(no data) ppb by weight	(no data) atoms relative to C = 1000000

Physical properties Read more »

• Density of solid: 20450 kg m^-3
• Molar volume: 11.59 cm³
• Thermal conductivity: 6 W m^‑1 K^‑1

Heat properties Read more »

• Melting point: 910 [637 °C (1179 °F)] K
• Boiling point: 4300 [ca. 4000 °C (7232 °F)] K
• Enthalpy of fusion: 10 kJ mol^-1

Crystal structure Read more »

The solid state structure of neptunium is: orthorhombic.

Neptunium: orbital properties Read more »

Neptunium atoms have 93 electrons and the shell structure is 2.8.18.32.22.9.2. The ground state electronic configuration of neutral Neptunium is [Rn].5f⁴.6d¹.7s² and the term symbol of Neptunium is ⁶L_11/2.

• Pauling electronegativity: 1.36 (Pauling units)
• First ionisation energy: 604.5 kJ mol^‑1
• Second ionisation energy: (no data) kJ mol^‑1

Isolation

Isolation: coming soon!

Neptunium isotopes Read more »

Table. Stables isotopes of neptunium.

Isotope	Mass /Da	Natural abund. (atom %)	Nuclear spin (I)	Nuclear magnetic moment (μ/μN)
		nil