Thorium (Th) – Periodic Table (Element Information & More)

This is a SUPER easy guide on Thorium element.

In fact, the table mentioned below is the perfect information box (Which gives you every single detail about the Thorium element in Periodic table.)

So if you want to know anything about Thorium element, then this guide is for you.

Let’s dive right into it!

Thorium Element (Th) Information

Appearance	Silvery-white metallic appearance
State (at STP)	Solid
Position in Periodic table	Group: actinides, Period: 7, Block: f
Category	Inner transition metals
Atomic number or  Protons	90
Neutrons	142
Electrons	90
Symbol	Th
Atomic mass	232.04 u
Electrons arrangement or  Bohr model	2, 8, 18, 32, 18, 10, 2
Electronic configuration	[Rn] 6d2 7s2
Atomic radius	237 picometers (van der Waals radius)
1st Ionization energy	6.08 eV
Electronegativity	1.3 (Pauling scale)
Crystal structure	FCC (face centered cubic)
Melting point	2023 K or 1750 °C or 3182 °F
Boiling point	5061 K or 4788 °C or 8650 °F
Density	11.725 g/cm3
Main isotope	232Th
Who discovered Thorium and when?	Jons Jakob Berzelius (in 1829)
CAS number	7440-29-1

Thorium in Periodic table

Thorium element is in period 7 and in actinides group of the Periodic table. Thorium is the f-block element and it belongs to inner transition metals group.

Click on above elements (in Periodic table) to see their information or Visit Interactive Periodic Table (which shows names, symbol, atomic mass, electron configuration, electrons arrangement, etc. of all the elements)

Click on above elements (in Periodic table) to see their information

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Why is Thorium in Period 7?

Let me ask you a question.

How many shells does thorium have?

It’s 7. Right?

You have already seen the bohr model of thorium atom in the above table.

From the Bohr model, it can be found that the number of orbits or shells in thorium is 7. Hence, as thorium has 7 orbits, it lies in period 7 of the Periodic table. 

5 Interesting facts about Thorium

Interesting facts about thorium element are mentioned below.

1. The name “Thorium” was derived from “Thor” which is the name of the Norse god of thunder.
2. The concentration of thorium in the earth’s crust is approximately 6 ppm by weight.
3. The Thorium element was discovered by chemist Jons Jakob Berzelius in 1829.
4. Thorium is mostly mined from regions of Australia, Canada, United states of America, Russia and India.
5. Thorite, thorianite and monazite are the major minerals which contain thorium in higher concentrations.

Properties of Thorium

The physical and chemical properties of thorium element are mentioned below.

Physical properties of Thorium

Physical properties of thorium are mentioned below.

• Thorium is a solid metal having a silvery-white metallic appearance.
• The melting point of thorium is 1750 °C and its boiling point is 4788 °C.
• The crystal structure of thorium is FCC (face centered cubic).
• Thorium has many isotopes, but out of those isotopes, the most stable isotope is ²³²Th, which has a half-life of 14 billion years.
• The atomic mass of thorium is 232.04 u and its density is  11.725 g/cm³.

Chemical properties of Thorium

Chemical properties of thorium are mentioned below.

• Thorium reacts with atmospheric oxygen and it tarnishes slowly, which results in a black oxide layer on it.
• Thorium also reacts with hydrogen, sulfur and halogens like fluorine, chlorine, bromine, etc.
• The most common oxidation state of thorium is +4. But apart from this, it also exists in other oxidation states such as +1, +2 and +3.
• The powdered thorium metal is highly reactive and it can even ignite in air.
• The thorium metal shows a slow reaction with water.
• Thorium dissolves in hydrochloric acid.

Uses of Thorium

Uses of thorium are mentioned below.

• Thorium is used as an alloying element with magnesium to increase the strength of magnesium.
• Thorium dioxide (which is a compound of thorium) is added to glass to increase the refractive index of glass.
• Thorium dioxide is also used in manufacturing of ceramics that are resistant to higher temperatures.
• Nowadays, the commercial use of thorium is minimized due to its radioactive nature.
• The heat present inside the earth’s crust is because of thorium as well as uranium.

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External resources:

1. Thorium – Element information, properties and uses | Periodic Table. (n.d.). Thorium – Element Information, Properties and Uses | Periodic Table. https://www.rsc.org/periodic-table/element/90/thorium
2. Thorium – Wikipedia. (2013, October 4). Thorium – Wikipedia. https://en.wikipedia.org/wiki/Thorium
3. C&EN: IT’S ELEMENTAL: THE PERIODIC TABLE – THORIUM. (n.d.). C&EN: IT’S ELEMENTAL: THE PERIODIC TABLE – THORIUM. https://pubsapp.acs.org/cen/80th/thorium.html?
4. It’s Elemental – The Element Thorium. (n.d.). It’s Elemental – the Element Thorium. https://education.jlab.org/itselemental/ele090.html
5. Thorium – World Nuclear Association. (n.d.). Thorium – World Nuclear Association. https://world-nuclear.org/information-library/current-and-future-generation/thorium.aspx
6. P. (n.d.). Thorium | Th (Element) – PubChem. Thorium | Th (Element) – PubChem. https://pubchem.ncbi.nlm.nih.gov/element/Thorium
7. Thorium. (n.d.). Thorium. https://pubs.usgs.gov/of/2004/1050/thorium.htm
8. Thorium | CCDC. (n.d.). Thorium | CCDC. https://www.ccdc.cam.ac.uk/elements/thorium/