Neptunium
Definition and meaning of Neptunium in chemistry.
![Neptunium element card: symbol Np, atomic number 93, atomic mass [237], electron configuration [Rn] 5f⁴ 6d¹ 7s², oxidation states +5, Actinide, f-block, period 7, solid at room temperature.](/assets/images/terms/neptunium-chemical-element.webp)
Neptunium is a human-made radioactive element with the symbol Np and atomic number 93. It was the first transuranic element ever made in a lab. This highly reactive, silvery metal belongs to the actinide series on the periodic table.
In more detail
A transuranic element has an atomic number higher than 92. It sits just past uranium on the periodic table. Active nuclear reactors produce most neptunium today.
It forms as a radioactive byproduct while the reactor runs. This happens when uranium fuel rods absorb extra neutrons. Trace amounts of neptunium also exist naturally in deep uranium ores.
These natural traces form through rare changes caused by background neutrons. This process is called transmutation. Transmutation means one chemical element changes into a totally different element.
The most stable type of neptunium is neptunium-237. It has a very long half-life of over two million years. A half-life is the time it takes for half of a radioactive sample to break down.
Neptunium-237 breaks down by shooting out energetic alpha particles. Neptunium has a very complex chemistry. It can take on many different oxidation states, from +3 to +7.
An oxidation state tells us how many electrons an atom gains, loses, or shares. Neptunium easily forms many complex chemical compounds. These include oxides, halides, and ions mixed in water.
The pure metal takes three different solid crystal shapes. We call these different shapes allotropes. The metal changes between these shapes as it gets hotter.
Neptunium-237 creates a big problem for storing nuclear waste safely. It stays dangerous for a long time and moves easily through dirt and rock.
Key facts
| Field | General Chemistry |
|---|---|
| Symbol | Np |
| Atomic number | 93 |
| Atomic mass | [237] u |
| Category | Actinide |
| State at room temperature | Solid |
| Melting point | 644 degrees Celsius |
| Year discovered | 1940 |
Scientists hit neptunium-237 with neutrons to make a new isotope called plutonium-238. Plutonium-238 works as a vital heat and power source for deep space probes. These probes use special generators to turn the radioactive heat directly into electricity.
Frequently asked questions
Why is neptunium called a transuranic element?
It has an atomic number of 93, which is larger than uranium's 92. This means it comes right after uranium on the periodic table. Most transuranic elements are made in labs.
What are the main health risks of radioactive neptunium?
Its long half-life and alpha particle radiation make it very dangerous inside the body. Severe risks happen if someone accidentally eats or breathes in the material. This makes nuclear waste cleanup difficult.
Related terms
Sources & references
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