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Thulium (Tm) – Element 69 of the periodic table

Thulium (symbol Tm) is element number 69 of the periodic table and belongs to the “Lanthanide” category. Its atomic mass is about 168.93, and its phase under standard conditions is Solid. This element sits in period 6 and the f-block (Lanthanides) of the periodic table, and its electrons are arranged in shells of 2, 8, 18, 31, 8, 2. The short electron configuration of Thulium is [Xe] 4f¹³ 6s². Known uses of Thulium include Medical lasers, Radiation therapy and X-ray machines.

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Properties of Thulium

Atomic number
69
Chemical symbol
Tm
Atomic mass
168.93
Category
Lanthanide
Period
6
Block
f
Phase
Solid
Protons
69
Electrons
69
Neutrons (approx.)
100
Electron shells
2, 8, 18, 31, 8, 2
Outer-shell electrons
2
Discovered
Paul-Émile Lecoq de Boisbaudran (1879)

Electron configuration of Thulium

The electron configuration of Thulium (Tm), with 69 electrons, is shown below. The last shell (shell 6) is highlighted:

Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹³ 5s² 5p⁶ 6s²
Short configuration
[Xe] 4f¹³ 6s²
Last shell
6s²

What is electron configuration and how is it written?

Electron shells of Thulium

Distribution of 69 electrons of Thulium across shells K to P:

  1. K2
  2. L8
  3. M18
  4. N31
  5. O8
  6. P2

What is a lanthanide?

The lanthanides are the 15 elements from lanthanum to lutetium, part of the f-block, with very similar chemical properties; they are often grouped among the “rare earths”.

Uses of Thulium

Frequently asked questions about Thulium

What is the atomic number of Thulium?

The atomic number of Thulium (Tm) is 69; that is, every atom of it has 69 protons.

What is the electron configuration of Thulium?

The electron configuration of Thulium (Tm) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹³ 5s² 5p⁶ 6s²; in short form it is [Xe] 4f¹³ 6s², and its last shell is 6s².

What is the chemical symbol of Thulium?

The chemical symbol of Thulium is Tm.

Where is Thulium located in the periodic table?

Thulium is located in period 6 and the f-block (Lanthanides) and belongs to the “Lanthanide” category.

What is the atomic mass of Thulium?

The atomic mass of Thulium is about 168.93 (atomic mass units).

What is the phase of Thulium under normal conditions?

The phase of Thulium under standard conditions is Solid.

What are the uses of Thulium?

Uses of Thulium include Medical lasers, Radiation therapy and X-ray machines.

Who discovered Thulium?

Thulium was discovered by Paul-Émile Lecoq de Boisbaudran in 1879.

Elements in the same category as Thulium (Lanthanide)

Lanthanum (La)Cerium (Ce)Praseodymium (Pr)Neodymium (Nd)Promethium (Pm)Samarium (Sm)Europium (Eu)Gadolinium (Gd)Terbium (Tb)Dysprosium (Dy)Holmium (Ho)Erbium (Er)Ytterbium (Yb)Lutetium (Lu)

See all Lanthanides