Chemical Formula
Np
Background
Edwin McMillan and Philip H. Abelson first produced neptunium at the University of California in 1940. The scientists bombarded uranium-238 atoms with neutrons to chemically produce neptunium-239, which has a half-life of 2.3 days. However, a long-lived isotope of neptunium, neptunium-237 was produced by Glenn T. Seaborg and A. C. Wahl in 1942 while bombarding uranium-238 with fast neutrons in a 60-inch cyclotron. Several mg of neptunium-237 were obtained to study its properties in detail. The element was named after the planet Neptune.
Basic Information
| Name |
Neptunium |
| Symbol |
Np |
| Atomic number |
93 |
| Atomic weight |
237 amu |
| Standard state |
Solid at 298 K |
| CAS Registry ID |
7439-99-8 |
| Group name |
Actinoid |
| Period in periodic table |
7 |
| Block in periodic table |
f-block |
| Color |
Silvery metal |
| Classification |
Metallic |
| Melting point |
917 K (644°C or 1191°F) |
| Boiling point |
4175 K (3902°C or 7056°F) |
| Density |
20.25 g/cm3 |
| Phase at room temperature |
Solid |
Occurrence
Neptunium was considered to be entirely artificial when it was first discovered. Later, it was estimated that very small quantities of neptunium are present in the Earth’s crust. It can also be found in uranium ores.
Neptunium - Periodic Table of Videos
Isotopes
Neptunium has 20 isotopes ranging from 225Np to 244Np. All the isotopes are radioactive. Its longest-lived isotope is 237Np with a half-life of 2.14 million years followed by 236Np with a half-life of 154,000 years and 235Np with a half-life of 396.1 days.
Production
Neptunium can be produced by the reduction of neptunium trifluoride with hot barium or lithium metal in a nuclear reactor at 1200°C (2192°F).
Key Properties
The key properties of neptunium are listed below:
- It is a silvery radioactive synthetic metal
- It is extremely reactive with acids and oxygen
- It exists in five oxidations states from neptunium (III) to neptunium (VII).
Applications
Apart from research applications, neptunium is widely used in neutron detectors and nuclear reactors.
References
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