Difference Between Uranium and Thorium

Main Difference – Uranium vs Thorium

Uranium and Thorium are well known radioactive elements that can be found in nature in significant amounts. They belong to the actinide series of the f block of the periodic table. Both Uranium and Thorium are weakly radioactive elements and are composed of a number of radioactive isotopes. Since they are weakly radioactive, some isotopes of Uranium and Thorium have different applications. These chemical elements may also be hazardous due to their radioactivity. The main difference between Uranium and Thorium is that Uranium has a naturally occurring fissile isotope whereas Thorium has no fissile isotopes.

Key Areas Covered

1. What is Uranium
      – Definition, Radioactivity, Isotopes, Applications
2. What is Thorium
      – Definition, Radioactivity, Isotopes, Applications
3. What are the Similarities Between Uranium and Thorium
      – Outline of Common Features
4. What is the Difference Between Uranium and Thorium
      – Comparison of Key Differences

Key Terms: Fissile Material, Isotope, Radioactive Decay, Radioactivity, Thorium, Uranium

What is Uranium

Uranium is a radioactive chemical element that has the atomic number 92 and the symbol U. Uranium belongs to the group of actinides in the periodic table of elements. It is in the f block of the periodic table. The atomic weight of the most stable and abundant isotope of Uranium is about 238.02 amu. The electron configuration of Uranium can be given as [Rn]5f36d17s2.

At room temperature and pressure, Uranium is a solid metal. The melting point of Uranium is about 1132oC. The boiling point is about 4130oC. Uranium can have a few stable positive oxidation states since Uranium has 6 valence electrons.

There are several isotopes of Uranium. The most abundant isotope is Uranium-238. (The abundance is about 99%). Uranium-235 and Uranium-234 can also be found in nature. But they are present in trace amounts. Uranium-235 is very important among these isotopes since it is the only fissile isotope that is naturally occurring. Thus, Uranium is widely used in nuclear power plants and nuclear weapons.

Figure 1: Model of Uranium 235 Atom

Uranium-238 is called a fertile material since this element itself it is not fissile but can be made into an isotope that can sustain a chain reaction by some other method such as bombardment with a high-speed neutron.

Figure 2: Some Reactions of Uranium Oxides

Uranium element can form oxides. The salts of Uranium are water soluble. They may give different colors in aqueous solutions according to their oxidation states. Furthermore, Uranium can form halides such as UF4 and UF6. These fluorides are formed when Uranium metal reacts with HF (hydrogen fluoride) or F2 (Fluorine gas).

What is Thorium

Thorium is a radioactive chemical element that has the atomic number 90 and the symbol Th. Thorium belongs to the actinide series of the f block in the periodic table of elements. It is in solid state at room temperature and pressure. The electronic configuration of Thorium is [Rn]6d27s2. The atomic weight of the most stable and abundant isotope of Thorium is about 232.038 amu.

Figure 3: Chemical Structure of Thorium Atom

The melting point of Thorium is about 1750oC and the boiling point is about 4785oC. The most common oxidation state of Thorium is 4 since the number of valence electrons in Thorium is 4. But there can also be other oxidation states such as +3, +2 and +1. These are weak basic compounds.

Thorium has a number of isotopes. But the most stable and abundant isotope is Thorium-232. (The abundance is about 99%). Other isotopes are found in very trace amounts. Thorium is highly reactive and can form different compounds. Thorium can involve in the formation of inorganic and coordination compounds.

Since Thorium is more abundant than Uranium, Thorium can be used as an alternative for Uranium in nuclear power plants. However, Thorium is hazardous due to its radioactivity. But Thorium slowly decays and it tends to emit alpha radiation. Therefore, the exposure to Thorium for a short time may not cause any risk (because the alpha radiation cannot penetrate through our skin).

Similarities Between Uranium and Thorium

• Uranium and Thorium are radioactive elements.
• Both elements undergo alpha decay slowly.
• Both elements are in the actinide series of the f block of the periodic table of elements.
• Both elements have naturally occurring isotopes.
• Both chemical elements are used in nuclear power plants and nuclear weapons.

Difference Between Uranium and Thorium

Definition

Uranium: Uranium is a radioactive chemical element that has the atomic number 92 and the symbol U.

Thorium: Thorium is a radioactive chemical element that has the atomic number 90 and the symbol Th.

Melting Point and Boiling Point

Uranium: The melting point of Uranium is about 1132oC. The boiling point is about 4130oC.

Thorium: The melting point of Thorium is about 1750oC. The boiling point is about 4785oC.

Isotopes

Uranium: Uranium has several isotopes including a naturally occurring fissile isotope.

Thorium: Thorium has several isotopes but there are no naturally occurring fissile isotopes.

Number of Valence Electrons

Uranium: Uranium has 6 valence electrons.

Thorium: Thorium has 4 valence electrons.

Abundance

Uranium: Uranium is less abundant than Thorium.

Thorium: Thorium is more abundant than Uranium.

Conclusion

Uranium and Thorium are two of the three elements that can undergo radioactive decay significantly and are found in large amounts in nature comparatively. However, these are hazardous elements that can cause different diseases in our body due to their radioactivity. But exposure to a small quantity for a very short time period may not be that harmful since these elements tends to undergo alpha decay and decay occurs very slowly.

References:

1. “Thorium – Element information, properties and uses | Periodic Table.” Royal Society of Chemistry, Available here. Accessed 4 Sept. 2017.
2. “Uranium.” Wikipedia, Wikimedia Foundation, 31 Aug. 2017, Available here. Accessed 4 Sept. 2017.
3. Kirk Sorensen, Chief Technologist, Flibe Energy | Sep 28, 2016. “What’s the Difference Between Thorium and Uranium Nuclear Reactors?” Machine Design, 10 Oct. 2016, Available here. Accessed 4 Sept. 2017.

Image Courtesy:

1. “U-235” By Stefan-Xp – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Uranium-trioxide-formation” By InXtremis – Own work (CC BY-SA 3.0) via Commons Wikimedia
3. “1802359” (Public Domain) via Pixabay

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