Thulium (Tm) – Periodic Table (Element Information & More)

This is a SUPER easy guide on Thulium element.

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

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

Let’s dive right into it!

Thulium Element (Tm) Information

Appearance	Silvery gray metallic surface
State	Solid
Position in Periodic table	Group: lanthanides, Period: 6, Block: f
Category	Inner transition metals
Atomic number or  Protons	69
Neutrons	100
Electrons	69
Symbol	Tm
Atomic mass	168.93 u
Electrons arrangement or  Bohr model	2, 8, 18, 31, 8, 2
Electronic configuration	[Xe] 4f13 6s2
Atomic radius	227 picometers (van der Waals radius)
1st Ionization energy	6.184 eV
Electronegativity	1.25 (Pauling scale)
Crystal structure	HCP (hexagonal close packed)
Melting point	1818 K or 1545 °C or 2813 °F
Boiling point	2223 K or 1950 °C or 3542 °F
Density	9.32 g/cm3
Main isotope	169Tm
Who discovered Thulium and when?	Per Teodor Cleve (in 1879)
CAS number	7440-30-4

Thulium in Periodic table

Thulium element is in period 6 and in lanthanide group of the Periodic table. Thulium is the f-block element and it belongs to inner transition metals group.

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Why is Thulium in Period 6?

Let me ask you a question.

How many shells does thulium have?

It’s 6. Right?

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

From the Bohr model, it can be found that the number of orbits or shells in thulium is 6. Hence, as thulium has 6 orbits, it lies in period 6 of the Periodic table. 

Why is Thulium in f-block?

Before knowing this reason, first of all I want to ask you a simple question.

How can you determine the blocks-wise position of elements?

The simple answer: The elements will lie in the s, p, d or f block will completely depend upon the subshell in which the last electron will enter.

For example; the electron configuration of thulium is [Xe] 6s² 4f¹³.

So the last electron of thulium enters the f-subshell or f-orbital. 

Hence, thulium is the f-block element.

5 Interesting facts about Thulium

Interesting facts about thulium element are mentioned below.

1. The name Thulium came from the name “Thule” which is the earliest name of Scandinavia (a region in North Europe).
2. Thulium element was discovered by Per Teodor Cleve (in 1879).
3. Out of all the rare earth metals present on the periodic table, thulium is the rarest element.
4. The concentration of thulium in the earth’s crust is approximately 0.5 ppm by weight.
5. Thulium is obtained from the earth’s crust from minerals like monazite, xenotime, gadolinite, etc.

Properties of Thulium

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

Physical properties of Thulium

Physical properties of thulium are mentioned below.

• Thulium is a malleable metal having a silver grey metallic appearance.
• Thulium is a soft metal that can be cut with a kitchen knife.
• The melting point of thulium is 1545 °C and its boiling point is 1950 °C.
• The atomic mass of thulium is 168.93 u and its density is 9.32 g/cm³.
• Thulium has many isotopes and out of those isotopes, the most abundant isotope is ¹⁶⁹Tm (having an abundance of almost 100%). Rest of the isotopes are synthetic isotopes that are prepared artificially in labs.

Chemical properties of Thulium

Chemical properties of thulium are mentioned below.

• As thulium is a chemically reactive metal, it is  not found in free state. But it is always found as a compound with other elements in the earth’s crust.
• When thulium is kept open in the air, it starts tarnishing.
• Thulium reacts with water to form hydroxide and it liberates hydrogen gas during this reaction.
• In compound form, the thulium is present in its trivalent state (i.e Tm³⁺).

Uses of Thulium

Uses of thulium are mentioned below.

• Thulium is used as an alloying metal with other rare earth elements to get the desired properties.
• As thulium gives blue fluorescence, it is also used in euro currency notes to detect the  fake notes.
• Thulium is also used for doping the fibre lasers.

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External resources:

1. P. (n.d.). Thulium | Tm (Element) – PubChem. Thulium | Tm (Element) – PubChem. https://pubchem.ncbi.nlm.nih.gov/element/Thulium
2. It’s Elemental – The Element Thulium. (n.d.). It’s Elemental – the Element Thulium. https://education.jlab.org/itselemental/ele069.html
3. Thulium – Wikipedia. (2009, June 6). Thulium – Wikipedia. https://en.wikipedia.org/wiki/Thulium
4. Thulium – Element information, properties and uses | Periodic Table. (n.d.). Thulium – Element Information, Properties and Uses | Periodic Table. https://www.rsc.org/periodic-table/element/69/thulium
5. C&EN: IT’S ELEMENTAL: THE PERIODIC TABLE – THE LANTHANIDES. (n.d.). C&EN: IT’S ELEMENTAL: THE PERIODIC TABLE – THE LANTHANIDES. https://pubsapp.acs.org/cen/80th/lanthanides.html?