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Thallium (Tl) – Element 81 of the periodic table

Thallium (symbol Tl) is element number 81 of the periodic table and belongs to the “Metal” category. Its atomic mass is about 204.38, and its phase under standard conditions is Solid. This element sits in period 6 and group 13 of the periodic table, and its electrons are arranged in shells of 2, 8, 18, 32, 18, 3. The short electron configuration of Thallium is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹. Known uses of Thallium include Electronics, Glassmaking and Medical research.

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Properties of Thallium

Atomic number
81
Chemical symbol
Tl
Atomic mass
204.38
Category
Metal
Period
6
Group
13
Phase
Solid
Protons
81
Electrons
81
Neutrons (approx.)
123
Electron shells
2, 8, 18, 32, 18, 3
Outer-shell electrons
3
Discovered
William Crookes (1861)

Electron configuration of Thallium

The electron configuration of Thallium (Tl), with 81 electrons, is shown below. The last shell (shell 6) is highlighted:

Full configuration
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹
Short configuration
[Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹
Last shell
6s² 6p¹

What is electron configuration and how is it written?

Electron shells of Thallium

Distribution of 81 electrons of Thallium across shells K to P:

  1. K2
  2. L8
  3. M18
  4. N32
  5. O18
  6. P3

What is a metal?

The p-block metals (the post-transition metals) are usually softer than the transition metals and have lower melting points.

Uses of Thallium

Frequently asked questions about Thallium

What is the atomic number of Thallium?

The atomic number of Thallium (Tl) is 81; that is, every atom of it has 81 protons.

What is the electron configuration of Thallium?

The electron configuration of Thallium (Tl) is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p¹; in short form it is [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p¹, and its last shell is 6s² 6p¹.

What is the chemical symbol of Thallium?

The chemical symbol of Thallium is Tl.

Where is Thallium located in the periodic table?

Thallium is located in period 6 and group 13 and belongs to the “Metal” category.

What is the atomic mass of Thallium?

The atomic mass of Thallium is about 204.38 (atomic mass units).

What is the phase of Thallium under normal conditions?

The phase of Thallium under standard conditions is Solid.

What are the uses of Thallium?

Uses of Thallium include Electronics, Glassmaking and Medical research.

Who discovered Thallium?

Thallium was discovered by William Crookes in 1861.

Elements in the same category as Thallium (Metal)

Aluminum (Al)Gallium (Ga)Indium (In)Tin (Sn)Lead (Pb)Bismuth (Bi)Polonium (Po)Nihonium (Nh)Flerovium (Fl)Moscovium (Mc)Livermorium (Lv)

See all Post-transition metals

Thallium’s group 13 neighbours

Boron (B)Aluminum (Al)Gallium (Ga)Indium (In)Nihonium (Nh)

Group 13 of the periodic table